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NBME 21 Answers

Block 1/Question#1
A 24-year-old woman with sickle cell disease comes to the ...
Serum parvovirus B19 IgM antibody test

Block 1/Question#2
A 6-month-old girl is brought to the physician because her ...
GM2

Block 1/Question#3
An investigator is studying the efficacy of distinct vaccine ...
Flagellin

Block 1/Question#4
A 67-year-old man comes to the emergency department because ...
Translation

Block 1/Question#5
A 45-year-old woman is brought to the emergency department 45 ...
Absorption atelectasis

Block 1/Question#6
A normal-appearing 17-year-old girl has never had a menstrual ...
Androgen insensitivity syndrome

Block 1/Question#7
A 30-year-old primigravid woman at 22 weeks' gestation comes ...
Listeria monocytogenes

Block 1/Question#8
A 52-year-old woman is admitted to the hospital because of ...
Speak with the two gynecologists to attempt to coordinate care

Block 1/Question#9
A 53-year-old woman who underwent an operation for breast ...
Breast: antagonist; Uterus: partial agonist

Block 1/Question#10
A 34-year-old woman is brought to the emergency department 30 ...
Primary metabolic acidosis with increased anion gap

Block 1/Question#11
A 27-year-old primigravid woman at 34 weeks' gestation is ...
Schistocytes

Block 1/Question#12
A 25-year-old nulligravid woman comes to the physician ...
Endometrial hyperplasia

Block 1/Question#13
A 25-year-old man develops shortness of breath after moving ...
Decreased alveolar Po2

Block 1/Question#14
A 21-year-old man is brought to the emergency department 45 ...
Streptococcus pneumoniae

Block 1/Question#15
A 35-year-old man comes to the physician because of a 1-day ...
Increased vascular permeability

Block 1/Question#16
A 43-year-old man comes to the physician for a follow-up ...
Aortic

Block 1/Question#17
A 7-year-old girl is brought to a clinic in a developing ...
Methionine

Block 1/Question#18
A 61-year-old woman is brought to the physician by her ...
Donepezil

Block 1/Question#19
A 22-year-old man has had frequent episodes of cutaneous ...
C1 esterase inhibitor (binds activated C1r, C1s)

Block 1/Question#20
A 10-year-old girl develops fever, malaise, and loss of ...
Retrograde transport through nerves

Block 1/Question#21
A 40-year-old man with type 2 diabetes mellitus comes to the ...
Stimulation of the peroxisome proliferator-activated receptor γ

Block 1/Question#22
A 36-year-old man with AIDS elects to participate in a ...
Chemokine

Block 1/Question#23
A 59-year-old man comes to the physician because of a 3-month ...
Foci of keratinization

Block 1/Question#24
A 23-year-old man drinks alcohol heavily on a weekend. Which ...
Fatty change

Block 1/Question#25
A 28-year-old man is brought to the emergency department 30 ...
Dissecting aneurysm

Block 1/Question#26
A 62-year-old man who is a farmer comes to the physician ...
Actinic keratosis

Block 1/Question#27
A 60-year-old man is brought to the emergency department ...
Urethral disruption

Block 1/Question#28
A 47-year-old man is brought to the emergency department by ...
Mixed venous oxygen tension

Block 1/Question#29
A 34-year-old man comes to the physician because of a 2-week ...
Cluster headache

Block 1/Question#30
A newborn has female external genitalia and a 46,XY ...
Dihydrotestosterone

Block 1/Question#31
A 30-year-old woman comes to the office for a follow-up ...
Linoleic acid

Block 1/Question#32
A 50-year-old man has had progressive dyspnea on exertion ...
Usual interstitial pneumonitis

Block 1/Question#33
A 30-year-old man comes to the physician because of a ...
Varicella-zoster virus infection

Block 1/Question#34
A 30-year-old man develops urinary incontinence 2 weeks after ...
Pelvic nerves

Block 1/Question#35
A 7-year-old boy is brought to the physician by his mother ...
Increased blood lead

Block 1/Question#36
A 51-year-old woman comes to the physician because of a ...
Area labeled 'B' (Parietal cell)

Block 1/Question#37
A 35-year-old man with diabetic ketoacidosis has a decrease ...
Serum potassium concentration

Block 1/Question#38
A 47-year-old woman with aplastic anemia is being treated for ...
Amphotericin B

Block 1/Question#39
A 33-year-old woman comes to the physician because of fever, ...
Genital herpes

Block 1/Question#40
A physician prescribes a recently marketed drug for 20 ...
Phase 4

Block 1/Question#41
A 35-year-old woman comes to the physician because of a 2-day ...
Uroporphyrinogen decarboxylase

Block 1/Question#42
A 36-year-old woman undergoes a total hysterectomy and ...
Hyperplasia

Block 1/Question#43
A 52-year-old man is brought to the emergency department 30 ...
Histamine

Block 1/Question#44
A test has been developed to screen for human papillomavirus ...
Predictive value of a positive test

Block 1/Question#45
An 18-year-old man comes to the physician because of a 2-week ...
Pyruvate kinase

Block 1/Question#46
A 66-year-old man is brought to the emergency department ...
Lipopolysaccharide stimulation of toll-like receptor

Block 1/Question#47
A 26-year-old woman (III-2) comes to the physician for ...
50% in females but near 0 in males

Block 1/Question#48
A 44-year-old man is admitted to the hospital because of ...
Increasing cGMP

Block 1/Question#49
An 80-year-old woman comes to the emergency department ...
Hydrochlorothiazide

Block 1/Question#50
A photograph is shown of a myelin-stained cross section of a ...
Loss of sensation to vibration over both feet

Block 2/Question#1
A 27-year-old man comes to the physician for an examination ...
Schizoid

Block 2/Question#2
A 4-year-old girl is conscious but unable to breathe ...
Pseudocholinesterase deficiency

Block 2/Question#3
A 17-year-old boy returns to the locker room after football ...
Apocrine

Block 2/Question#4
An 18-year-old woman comes to the office because of a 2-week ...
Extensor carpi radialis brevis

Block 2/Question#5
A 2-week-old male newborn has a patent ductus arteriosus. ...
Higher than normal left ventricular cardiac output

Block 2/Question#6
A 38-year-old woman comes to the physician because of a ...
Serum calcium concentration

Block 2/Question#7
A 50-year-old man with rheumatoid arthritis comes to the ...
Anemia of chronic disease

Block 2/Question#8
A 55-year-old man is diagnosed with renal artery stenosis. ...
Cortex

Block 2/Question#9
A 40-year-old man is brought to the emergency department 45 ...
Metabolic acidosis and respiratory acidosis

Block 2/Question#10
A 42-year-old woman comes to the physician because of a ...
Rosacea

Block 2/Question#11
A 22-year-old woman, gravida 1, para 1, is brought to the ...
Internal iliac

Block 2/Question#12
A 66-year-old woman comes to the physician because of fever, ...
Diverticulitis

Block 2/Question#13
A 53-year-old woman with gastroesophageal reflux disease ...
Omeprazole

Block 2/Question#14
A 30-year-old woman comes to the office because she is ...
Abnormal brain development

Block 2/Question#15
A 48-year-old man is brought to the emergency department ...
Splenic and left renal

Block 2/Question#16
A 34-year-old woman comes to the physician because of a ...
Atrioventricular bundle

Block 2/Question#17
Scientists have identified the flawed gene that causes about ...
Mismatch repair

Block 2/Question#18
A 34-year-old woman comes to the physician because she has ...
“I’m concerned about how bad you’ve been feeling lately. Have you had any thoughts about death or wanting to be dead?”

Block 2/Question#19
A 3-year-old boy who recently immigrated to the USA is ...
Increased proportions of osteoid

Block 2/Question#20
A 14-year-old girl is brought to the physician by her mother ...
Trichotillomania

Block 2/Question#21
A 35-year-old woman undergoes flexible nasopharyngoscopy ...
Superior to the superior concha

Block 2/Question#22
A 33-year-old woman, gravida 4, para 4, is admitted to the ...
Transfusion-related acute lung injury

Block 2/Question#23
A 4-year-old boy with chronic granulomatous disease is ...
Macrophages producing interleukin-1 (IL-1)

Block 2/Question#24
A 65-year-old man dies in a motor vehicle collision. A ...
Squamous cell carcinoma

Block 2/Question#25
A 54-year-old man comes to the physician for a routine health ...
Area labeled 'F' (Efferent arteriole)

Block 2/Question#26
A healthy 32-year-old woman at 35 weeks' gestation is ...
Birth canal reflex

Block 2/Question#27
A 47-year-old woman with psoriasis comes to the physician for ...
“Most people find it difficult to stick to a routine. How did you do?”

Block 2/Question#28
A 64-year-old woman with type 2 diabetes mellitus and ...
Gemfibrozil

Block 2/Question#29
A healthy 25-year-old man is participating in a study of ...
Alanine

Block 2/Question#30
A 44-year-old man comes to the physician because of ...
Leukotriene C4: increased;
Arachidonic acid: increased;
Prostaglandin H2: decreased;
Prostaglandin E2: decreased


Block 2/Question#31
A 37-year-old man is brought to the emergency department 45 ...
Intercostal

Block 2/Question#32
A 17-year-old boy has the acute onset of lethargy, sore ...
Lymphocytes

Block 2/Question#33
A 68-year-old man comes to the physician because of a 1-month ...
Libido: normal; Nocturnal erections: normal

Block 2/Question#34
A 28-year-old man is brought to the emergency department ...
Inferior rectus and inferior oblique

Block 2/Question#35
A 4-month-old female infant is brought to the emergency ...
Hyponatremia

Block 2/Question#36
An investigator is conducting a study of antiretroviral ...
Enfuvirtide

Block 2/Question#37
A 17-year-old boy is evaluated for constitutional delay in ...
Craniopharyngioma

Block 2/Question#38
A 63-year-old man with bladder cancer starts treatment with ...
Tubulin polymerization stabilization

Block 2/Question#39
A 64-year-old man with bronchospastic pulmonary disease ...
Enhanced action of the agonist at β-adrenergic receptors

Block 2/Question#40
Acetaminophen and nonsteroidal antiinflammatory agents reduce ...
Prostaglandin E2

Block 2/Question#41
A 75-year-old woman has the sudden onset of Horner syndrome ...
Posterior inferior cerebellar

Block 2/Question#42
A 26-year-old man with HIV infection comes to the physician ...
Penicillin

Block 2/Question#43
A 78-year-old woman is brought to the emergency department by ...
Embolectomy

Block 2/Question#44
A 75-year-old man has the sudden onset of partial loss of ...
Parietal lobe, left

Block 2/Question#45
A 3-year-old boy is brought to the emergency department ...
Synthesis of factor X (Stuart factor)

Block 2/Question#46
An 8-year-old girl is brought to the physician for a ...
“Your daughter’s development is normal.”

Block 2/Question#47
A 55-year-old woman comes to the physician because of a ...
Increased parathyroid hormone

Block 2/Question#48
A 75-year-old man has fever, back pain, and pain on ...
Enterococcus faecalis

Block 2/Question#49
A 6-year-old girl is brought to the physician by her mother ...
Poxvirus

Block 2/Question#50
A 65-year-old woman comes to the emergency department because ...
Lung and common carotid artery

Block 3/Question#1
A 30-year-old woman develops dimness of vision
Ethambutol

Block 3/Question#2
A 40-year-old man with interstitial pulmonary fibrosis has a ...
Increased radial traction on airways

Block 3/Question#3
A 55-year-old African American man with hypertension is asked ...
Tell the patient that he can change his mind about participating

Block 3/Question#4
A clinical trial is conducted to compare the efficacy of a ...
Surgical procedure group: 400; Medical management group: 400

Block 3/Question#5
A 70-year-old woman is found to have persistent fever despite ...
Candida albicans

Block 3/Question#6
A 40-year-old African American woman comes to the physician ...
1,25-Dihydroxycholecalciferol

Block 3/Question#7
A 65-year-old man comes to the physician because of a 1-month ...
DNA fragmentation

Block 3/Question#8
A 55-year-old woman is brought to the emergency department by ...
Mammillary bodies

Block 3/Question#9
A 75-year-old woman is brought to the emergency department ...
Shrunken eosinophilic (red) neurons

Block 3/Question#10
A 30-year-old man has had intermittent severe lower abdominal ...
Cysteine

Block 3/Question#11
A 50-year-old man is found dead in bed at home. His family ...
Arrhythmia

Block 3/Question#12
A 55-year-old man with hypertension comes to the physician ...
Left renal artery atherosclerosis

Block 3/Question#13
A 40-year-old woman comes to the physician for an initial ...
Antagonizes VLDL-cholesterol secretion

Block 3/Question#14
A 35-year-old man is brought to the emergency department ...
Activation of adenylyl cyclase

Block 3/Question#15
A 47-year-old man has jaundice. Laboratory findings include ...
Obstruction of the bile duct

Block 3/Question#16
A 16-year-old boy is brought to the physician because of a ...
Exercise-induced asthma

Block 3/Question#17
A 66-year-old woman with pancreatic cancer comes to the ...
Short gastric

Block 3/Question#18
An 83-year-old man comes to the physician because of a 3-day ...
Bullous pemphigoid antigen

Block 3/Question#19
A 25-year-old woman develops increasing shortness of breath ...
Four-chamber dilation

Block 3/Question#20
A 68-year-old woman has had a fever and shortness of breath ...
Reactive granulocytosis

Block 3/Question#21
A screening program is instituted for detection of vaginal ...
10%

Block 3/Question#22
A 9-year-old boy has mild mental retardation and a 4-year ...
Rhabdomyoma

Block 3/Question#23
A 43-year-old woman dies after a 10-year illness ...
Area labeled ‘C’ (Caudate nucleus)

Block 3/Question#24
Diastolic blood pressures are obtained in two groups of 100 ...
Median of group Y: higher; Mode of group Y: higher

Block 3/Question#25
A 32-year-old woman comes to the physician because her sister ...
Dysplastic nevi

Block 3/Question#26
A 19-year-old woman comes to the office because of a 1-month ...
Descending colon

Block 3/Question#27
A 55-year-old woman with a benign nodule in the left lobe of ...
External carotid

Block 3/Question#28
A 1-year-old girl is admitted to the hospital because of a ...
Disruption of the secondary structure of collagen molecules

Block 3/Question#29
A 34-year-old man is evaluated after becoming light-headed ...
Number of impulses from carotid baroreceptor: decreased;
Sympathetic efferent activity: increased;
Parasympathetic efferent activity: decreased


Block 3/Question#30
A 41-year-old man comes to the physician because of a 6-week ...
Abduction of the upper extremity

Block 3/Question#31
A 28-year-old woman at 18 weeks' gestation has palpitations. ...
Free T4

Block 3/Question#32
A 72-year-old man comes to the physician because of a 2-week ...
Bleomycin

Block 3/Question#33
Left radial arterial and venous blood samples are drawn from ...
HCO3 transported in the plasma

Block 3/Question#34
A 39-year-old woman with rheumatoid arthritis develops ...
Membranous glomerulonephritis

Block 3/Question#35
A 63-year-old woman comes to the physician because of a 5-day ...
Increased resting cardiac output

Block 3/Question#36
Which of the following best explains why the use of an ...
Myeloma cells do not have membrane-bound surface immunoglobulin

Block 3/Question#37
A 5-year-old boy who has homocystinuria improves with ...
The line on the graph labeled ‘B’

Block 3/Question#38
A 28-year-old man develops a temperature of 39.9°C (103.8°F) ...
Granulocyte colony-stimulating factor

Block 3/Question#39
A 74-year-old woman with mild dementia is admitted to the ...
Inability to understand the severity and prognosis of her medical condition

Block 3/Question#40
A 65-year-old woman undergoes surgical repair of an aneurysm ...
Area labeled ‘A’ (Cranial nerve 3)

Block 3/Question#41
A 75-year-old woman comes to the physician's office because ...
Major depressive disorder

Block 3/Question#42
A 27-year-old primigravid woman at 39 weeks' gestation is ...
Shoulder dystocia

Block 3/Question#43
An undernourished 70-year-old man has fever, night sweats, ...
Interferon-γ

Block 3/Question#44
A 23-year-old woman develops persistent sneezing each year in ...
Stabilization of mast cell membranes

Block 3/Question#45
A 28-year-old man comes to the physician for evaluation of ...
Fructose

Block 3/Question#46
A 38-year-old woman comes to the physician because of a ...
Patent foramen ovale

Block 3/Question#47
A 48-year-old man comes to the physician because of ...
Increased intestinal iron absorption

Block 3/Question#48
A 29-year-old woman comes to the physician because of a ...
Baclofen

Block 3/Question#49
The gene that codes for a protein normally found in the ...
Deletion of a hydrophobic amino acid sequence from the N terminus

Block 3/Question#50
A 32-year-old woman comes to the emergency department because ...
Arthropod vector

Block 4/Question#1
A 50-year-old woman has azotemia. Renal ultrasonography shows ...
Uterine cervix

Block 4/Question#2
A 23-year-old woman comes to the student health center ...
Obliterative endarteritis with lymphocytes and plasma cells

Block 4/Question#3
A study was performed that evaluated the relationship between ...
Odds ratio

Block 4/Question#4
The FOXO transcription factor responds to insulin signaling ...
Nuclear/cytoplasmic shuttling: yes;
Serine phosphorylation: yes
Ubiquitin-mediated proteolysis: no


Block 4/Question#5
An 11-year-old boy has had persistent pain in his right knee ...
Lung

Block 4/Question#6
A 55-year-old man comes to the physician because of a 2-month ...
Cortisol

Block 4/Question#7
A 14-year-old boy is brought to the physician by his mother ...
Inhaled glue

Block 4/Question#8
A 70-year-old woman has had recurrent pneumonia, fatigue, and ...
Euthyroid sick syndrome

Block 4/Question#9
A 60-year-old woman with psoriasis comes to the physician ...
Porphyria cutanea tarda

Block 4/Question#10
A 64-year-old man is evaluated for cough, dyspnea, and chest ...
Hyponatremia

Block 4/Question#11
A study is conducted on patients with asthma to compare a new ...
If the treatment really changes the mean asthma score by 0.4, there is an 80% chance that a study of this size will find a p-value < 0.05

Block 4/Question#12
A 24-year-old man with a history of drug abuse has nausea, ...
Heroin

Block 4/Question#13
A 4-month-old boy is diagnosed with a rare autosomal ...
Dilated rough endoplasmic reticulum

Block 4/Question#14
A 25-year-old woman has a 3-week history of bleeding gums ...
Autoantibodies against platelet glycoproteins

Block 4/Question#15
A 5-year-old boy is brought to the physician for a well-child ...
Lack of choroidal pigment deposition in the macula

Block 4/Question#16
A 40-year-old woman who had pneumonia due to Streptococcus ...
Surfactant

Block 4/Question#17
A 48-year old man is referred for evaluation of possible ...
Increase in width

Block 4/Question#18
A previously healthy 4-week-old male newborn is brought to ...
Pyloric stenosis

Block 4/Question#19
A 45-year-old woman comes to the emergency department because ...
Hepatopancreatic ampulla

Block 4/Question#20
A 7-month-old boy is brought to the physician 2 days after ...
46,XY

Block 4/Question#21
A 47-year-old man is treated with colchicine for acute gouty ...
Tubulin polymerization

Block 4/Question#22
A 57-year-old woman is brought to the emergency department ...
Ninth

Block 4/Question#23
An investigator is studying the regulation of pulmonary ...
Intravenous infusion of 0.9% saline for 5 minutes

Block 4/Question#24
A 56-year-old man undergoes a renal transplant. Five minutes ...
IgG plus complement

Block 4/Question#25
An 80-year-old woman cannot concentrate her urine above 450 ...
2.0

Block 4/Question#26
The immunosuppressive agent cyclosporin A (CsA) is a potent ...
Interleukin-2 (IL-2) gene transcription

Block 4/Question#27
A 65-year-old woman is being treated in the hospital for ...
“The two of you seem to have a very important relationship. Of course you may stay together.”

Block 4/Question#28
A 56-year-old man undergoes surgical resection of the ...
Release of cholecystokinin

Block 4/Question#29
A 22-year-old man comes to the physician because of a 2-month ...
Formation of destructive free radicals

Block 4/Question#30
A 5-year-old boy is admitted to the hospital because of ...
ApoC-II

Block 4/Question#31
A 48-year-old woman comes to the physician because of a ...
Paracrine stimulation of osteoclasts by osteoblasts

Block 4/Question#32
A 19-year-old college student says he hears voices." He was ...
Risperidone

Block 4/Question#33
A female newborn delivered at 26 weeks' gestation is found to ...
Retina

Block 4/Question#34
A healthy 8-year-old boy is brought to the physician by his ...
Stimulation of the release of biogenic amine neurotransmitters

Block 4/Question#35
A 50-year-old woman is admitted to the hospital because of a ...
Didanosine (ddI)

Block 4/Question#36
A 45-year-old man comes to the physician because of ...
Chondrosarcoma

Block 4/Question#37
A 66-year-old right-handed woman develops the acute onset of ...
Area labeled 'B' (Internal capsule)

Block 4/Question#38
A 62-year-old woman is brought to the physician by her ...
Instruct the patient to keep notes and lists to help her memory

Block 4/Question#39
A 46-year-old man comes to the physician because of a 2-month ...
1/15

Block 4/Question#40
A study is conducted to assess the normal mean serum urea ...
500 Men from a list of patients scheduled to be examined by a urologist

Block 4/Question#41
A 66-year-old man with stage IV colon cancer comes to the ...
Loperamide

Block 4/Question#42
A 20-year-old primigravid woman at 12 weeks' gestation comes ...
Multifactorial

Block 4/Question#43
A 4-year-old boy falls and lacerates his lower leg to the ...
Formation of fibrin clot

Block 4/Question#44
A 28-year-old woman with chronic renal failure (creatinine ...
Furosemide

Block 4/Question#45
During an experiment, an investigator observes that glutamate ...
NMDA receptors are blocked by Mg2+ at the resting membrane potential

Block 4/Question#46
A 14-year-old girl is brought to the physician for a ...
TP53

Block 4/Question#47
While lifting weights, a 24-year-old man develops a painful ...
Strangulation

Block 4/Question#48
A 75-year-old man with dementia, Alzheimer type, is brought ...
Encourage the family to come to a consensus based on their perception of the patient's wishes

Block 4/Question#49
A 76-year-old man comes to the physician because of a 2-week ...
Left thalamus

Block 4/Question#50
A 19-year-old woman is brought to the emergency department 30 ...
Scaphoid

Recent comments ...

... nosancuck made a comment on nbme21/block1/q#5 (A 45-year-old woman is brought to the emergency...)
 +28  upvote downvote
submitted by nosancuck(43)

Bruh let me tell you a lil secret

PEEP prevents Atelectasis AKA dat LUNG COLLAPSE

Dont be worryin about random words they puts in front of the HIGH YIELD ones

hungrybox  literally LOL'd lmao I love this
... assoplasty made a comment on nbme21/block3/q#31 (A 28-year-old woman at 18 weeks' gestation has...)
 +27  upvote downvote
submitted by assoplasty(42)

I think the concept they’re testing is the increased TBG levels in pregnancy, and not just hyperthyroidism in general.

When screening for hypo/hyperthyroidism, TSH levels are ALWAYS preferentially checked because they are more sensitive to minute differences in T3/T4. Often times TSH levels can demonstrate a change even when T3/T4 levels are in the subclinical range. The only exception to this would be in pregnancy (and I guess maybe liver failure? I doubt they would ask this though). High estrogen levels prevents the liver from breaking down TBG, leading to increased TBG levels in the serum. This binds to free T4, decreasing the amount of available free T4. As a compensatory mechanism, TSH levels are transiently increased and the RATE of T4 production is increased to replenish baseline free T4 levels. However the TOTAL amount of T4 is increased.

The question is asking how to confirm hyperthyroidism in a pregnant woman --> you need to check FREE T4 levels (because they should be normal due to compensatory response). You cannot check TSH (usually elevated in pregnancy to compensate for increased TBG), and you cannot check total T4 levels (will be increased). You got the answer right either way but I think this is a different reasoning worth considering, because they can ask this concept in other contexts of hyper-estrogenism, and if they listed “TSH” as an answer choice that would be incorrect.

hungrybox  Extremely thorough answer holy shit thank u so much I hope you ACE Step 1
arkmoses  great answer assoplasty, I remember goljan talking about this in his endo lecture (dudes a flippin legend holy shit) but it kinda flew over my head! thanks for the break down!
whoissaad  you mean total amount of T4 is "not changed"? 2nd para last sentence.
ratadecalle  @whoissaad, in a normal pregnancy total T4 is increased, but the free T4 will be normal and rest of T4 bound to TBG. If patient is hyperthyroid, total T4 would still be increased but the free T4 would now be increased as well.
maxillarythirdmolar  To take it a step further, Goljan mentions that there are a myriad of things circulating in the body, often in a 1:2 ratio of free:bound, so in states like this you could acutally see disruption of this ratio as the body maintains its level of free hormone but further increases its level of bound hormone. Goljan also mentions that you'd see the opposite effect in the presence of steroids and nephrotic syndromes. So you could see decreased total T4 but normal free T4 because the bound amounts go down.
... lnsetick made a comment on nbme21/block2/q#3 (A 17-year-old boy returns to the locker room after...)
 +27  upvote downvote
submitted by lnsetick(38)
  • APocrine = your armpits smell like an APE
  • ceRUMen = there’s no ROOM in your ears since they’re full of wax
  • EC-CRYne = when you ECercise, your pores are CRYing
  • SEBaceous = SEBum is SEEPing out of your pores
hungrybox  as an ape i'm offended
dr.xx  stop being an ape. evolutionize!
dbg  as a creationist i'm offended
maxillarythirdmolar  Also, Tarsal/Meibomian glands are found along the rims of the eyelid and produce meibum
... drdoom made a comment on nbme21/block3/q#49 (The gene that codes for a protein normally found in...)
 +22  upvote downvote
submitted by drdoom(215)

The synthesis of virtually all proteins (mRNA->peptide) occurs in the cytoplasm.[1] That’s where all ribosomes reside, after all. Ribosomes, which are mostly just rRNA (~2/3 rRNA + 1/3 protein*, by weight), are assembled in the nucleus but only do their stuff once they get to the cytoplasm.

For a protein to leave its original hometown of the cytosol and become a resident of the nucleus or, sayyyyyy, the endoplasmic reticulum, it needs to have a little string of amino acids which shout “I belong in the nucleus!” or “I belong in the endoplasmic reticulum!”

Proteins ultimately destined for the ER contain an unimaginatively named string of amino acids known as “signal sequence,” which, for the purposes of the Step 1, is always at the N-terminus. The signal sequence tells other cytosolic proteins, “Hey! Take me (and the rest of the peptide of which I am part) to the ER!”

In the absence of this signal, a protein will remain in its “default” home of the cytosol.

Here’s a nice schematic showing the flow of proteins from initial synthesis to final destinations:


Endnotes

  1. “The synthesis of virtually all proteins in the cell begins on ribosomes in the cytosol.” (Essential Cell Biology, Alberts et al., 2014, p. 492)

*If you really want your mind blown, consider that even the protein subunits that make up that 1/3 of a ribosome are themselves initially synthesized in the cytosol; later, they are transported back into the nucleus via the nuclear pore.

... hayayah made a comment on nbme21/block3/q#33 (Left radial arterial and venous blood samples are...)
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submitted by hayayah(422)

the majority of carbon dioxide molecules are carried as part of the bicarbonate buffer system. In this system, carbon dioxide diffuses into the RBCs. Carbonic anhydrase (CA) within RBCs quickly converts the carbon dioxide into carbonic acid (H2CO3). Carbonic acid is an unstable intermediate molecule that immediately dissociates into bicarbonate ions (HCO3-) and hydrogen (H+) ions.

The newly synthesized bicarbonate ion is transported out of the RBC into the plasma in exchange for a chloride ion (Cl−); this is called the chloride shift. When the blood reaches the lungs, the bicarbonate ion is transported back into the RBC in exchange for the chloride ion. The H+ ion dissociates from the hemoglobin and binds to the bicarbonate ion. This produces the carbonic acid intermediate, which is converted back into carbon dioxide through the enzymatic action of CA. The carbon dioxide produced is expelled through the lungs during exhalation.

hungrybox  Amazing explanation. Thank you!!
namira  in case anyone wants to visualize things... https://o.quizlet.com/V6hf-2fgWeaWYu1u23fryQ.png
ergogenic22  CO2 is carried in the blood is bound to hemoglobin, known as carbaminohemoglobin (HbCO2) (5%), dissolved CO2 (5%), bicarb is 90%
... mcl made a comment on nbme21/block1/q#16 (A 43-year-old man comes to the physician for a...)
hyperfukus  this link is great! they're still kind of close together :( its so hard to tell for me w/o reference of the others
hyperfukus  this link is great! they're still kind of close together :( its so hard to tell for me w/o reference of the others
... hungrybox made a comment on nbme21/block2/q#17 (Scientists have identified the flawed gene that...)
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submitted by hungrybox(250)

when diff single strand repair mechanisms are used:

  • repair newly synthesized strand: mismatch repair (Lynch syndrome)
  • repair pyrimidine dimers caused by dat UV exposure: nucleotide excision repair (Xeroderma pigmentosum)
  • repair spontaneous/toxic alteration: base excision repair
meningitis  Brca: recombinant repair
... jambo2222 made a comment on nbme21/block4/q#5 (An 11-year-old boy has had persistent pain in his...)
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submitted by jambo2222(14)

It’s an osteosarcoma. Sarcoma = hematogenous mets. It’s in the legs so think how a DVT goes to lung. Same idea.

tinydoc  Perfect way to remember it. Thank you!
chandlerbas  Iused the mnemonic PB (lead) KeTtLe....looking at the stem it said "osteolytic mass" meaning that it has to be either Breast, Kidney, thyroid or lungs. none of the rest are options leaving lungs. but jambo2222 very noiice that works too!
... hungrybox made a comment on nbme21/block1/q#49 (An 80-year-old woman comes to the emergency...)
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submitted by hungrybox(250)

Hydrochlorothiazide is a thiazide diuretic => thiazide diuretics are associated with hypokalemia.

What other diuretics are associated with hypokalemia? Loop diuretics.

Why?

Inhibition of Na+ reabsorption occurs in both loop diuretics (inhibit NKCC cotransporter) and thiazide diuretics (inhibit NaCl cortransporter). All of this increased Na+ increases Aldosterone activity.

Relevant to this problem, Aldosterone upregulates expression of the Na+/K+ ATP antiporter (reabsorb Na+ into body, expel K+ into lumen). This results in hypokalemia in the body.

Hang on, there's more high yield info!

Aldosterone does one other important thing - activation of a H+ channel that expels H+ into the lumen.

So, given that this patient has hypokalemia, you know there is upregulation of Aldosterone. Do you think her pH would be high, or low? Exactly, it would be high because inc. Aldosterone => inc. H+ expelled into the lumen => metabolic akalosis.

Now you understand why both loop diuretics and thiazide diuretics can cause what's called "hypokalemic metabolic alkalosis."

hungrybox  jesus this answer was probably too long i'm sorry
meningitis  I disagree. It's the complete thought process needed for many Thiazide/Loop question that can be thrown. Thanks.
amirmullick3  This is what NBME should be providing with each question's correct answer! Thanks hungrybox!
amirmullick3  @hungrybox did you mean "All of this DECREASED Na increases aldosterone activity."?
... notadoctor made a comment on nbme21/block1/q#32 (A 50-year-old man has had progressive dyspnea on...)
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submitted by notadoctor(62)

Usual interstitial pneumonitis is the histological definition of Idiopathic pulmonary fibrosis. We know that this patient has pulmonary fibrosis because the question states that there is fibrous thickening of the alveolar septa. This question was just testing that we knew the other names for Pulmonary Fibrosis.

aneurysmclip  Nbme back at it again
... assoplasty made a comment on nbme21/block2/q#29 (A healthy 25-year-old man is participating in a...)
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submitted by assoplasty(42)

Fats are ketogenic (except odd chain FA), so they produce ketones for energy production (Acetyl-CoA) rather than glucose. If the question asked what the primary source of energy production was, it would still be glycogen (and not ketones), because this is within 24 hours. However after 24 hours the answer could be ketone bodies. Regardless, the question specifically said the pt had a serum glucose of 100, indicating that we are looking for something that provides a substrate for gluconeogenesis.

During periods of starvation, substrates for gluconeogenesis come from two sources: (1) breakdown of existing muscle, or (2) via odd-chain FA through propionyl-CoA. (*Valine also feeds into propionyl CoA, but is not involved during starvation --> see below)

(1) The alanine-pyruvate cycle provides this (glutamine in muscle + pyruvate --> alanine --> goes to liver --> transamination to alpha-ketoglutorate --> pyruvate is separated from glutamine --> glutamine goes to urea cycle, pyruvate goes on to gluconeogenesis). Lactate can also be used (this could have been a right answer if it were listed).

(2) Odd chain FAs are also glucogenic, but stearic acid (provided in the answer choice) isn’t odd chain, so it is only ketogenic and can be ruled out.

Although valine (and other branched a.a.) feed into Propionyl-CoA, they are not used in starvation because starvation strictly relies on hepatic gluconeogenesis. These a.a. are not metabolized in the liver because the liver lacks branched-chain a.a. transferase enzyme. In First Aid, Biochem section, under Fasting/Starvation, in both the “fasting state” (which is within the time frame of this question), or the “starvation state,” both utilize hepatic gluconeogenesis. My assumption is that valine is used during regular metabolism, and not during periods of starvation.

hello  I want to re-emphasize something that @assoplasty has already stated :). The Q-stem states serum glucose = 100, and the Q asks why the patient is able to maintain normoglycemia. Therefore, you can immediately eliminate choices A and C because acetoacetate and beta-hydroxybutyrate are sources of energy during ketogenesis -- ketogenesis does not provide glucose energy sources.
chandlerbas  ^ this checks out: valine and isoleucine are broken down in the muscle into branched chain 2 oxo acid via branched chain aminotransferase (reversible) then the valine and isoleucine leave the muscle and swims to the liver to be acted on by branched chain 2 oxo acid DH (irreversible). So bascially the process from taking BCAA valine and isoleucine requires 2 enzymes. the first enzyme is in the muscle, and the second enzyme is in the liver (for simplification purposes --> both organs contain both enzymes but dont have the same affinity for their substrate). source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1147506/?page=4 so you're right to say that the liver
... niboonsh made a comment on nbme21/block4/q#45 (During an experiment, an investigator observes that...)
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submitted by niboonsh(84)

https://www.youtube.com/watch?v=4-DuvwoH2zQ if ur lazy like me, this is a good refresher video

d_holles  Amazing video dude. Somehow never learned this in neuro lol.
... g.liller@yahoo.com made a comment on nbme21/block3/q#5 (A 70-year-old woman is found to have persistent...)
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submitted by g.liller@yahoo.com(13)

Candida is a part of the normal flora of skin, could cause contamination of a central venous catheter. The question states that the organism is purple, budding, did not respond to broad spectrum antibiotics (aka they didn't use fluconazole or amphotericin B). Lastly, they showed it plated on blood agar and there was no hemolysis which eliminates staph (the only other possible contender here.)

Cryptococcus usually involves meningitis in immunocompromised pts. E. coli is gram negative sporothrix is usually transmitted by a thorn on a rose or someone with a history of gardening

hungrybox  Also, the yeast form of Candida is gram (+)
dr_jan_itor  I got thrown off by the part where they said "ovoid" and thought they were implying a cigar shape. I chose sporothrix for the morphology in spite of knowing that it clincally made no sense.
lilmonkey  I chose S. aureus before reading the question (looks like b-hemolysis). Then I saw "budding organisms" and picked the correct one.
... hayayah made a comment on nbme21/block4/q#23 (An investigator is studying the regulation of...)
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submitted by hayayah(422)

Lymph flow rate is usually low. It is influenced primarily by the rate of lymph formation. For example, if blood capillary pressure is increased by arterial vasodilation or venous constriction, the flow rate of lymph increases. Also, the flow rate is affected by compression of lymphatics by contraction of neighboring musculature and by negative intrathoracic pressure (breathing).

Interstitial pressure (so pressure in the ECF, which would increase if given IV saline) and lymph flow are positively related. A small increase in interstitial volume greatly increases its pressure, promoting lymph flow that acts to restore the interstitial volume to normal.

more on this topic: https://www.ncbi.nlm.nih.gov/books/NBK53448/

linwanrun1357  Do not understand the breathing (choice C and D) breath in and out are different?
... flashvoyger made a comment on nbme21/block4/q#25 (An 80-year-old woman cannot concentrate her urine...)
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submitted by flashvoyger(12)

The question is asking you how much water must the woman take in to maintain the same osmolality. This woman takes in 450 mOsm of solute per day. This is a unit of measurement -- think of it like grams.

For her to keep the same osmolality she must excrete 450 mOsm per day. The only way for her to excrete the solute is via the kidneys. The only way for her kidneys to excrete 450 mOsm is if they excrete 1 liter of water also. This is the max concentration that her kidneys can produce. (Her kidneys are not “powerful enough” to make her urine any more concentrated than that.)

This woman is also losing another liter of water to feces, sweating and respiration. This is the “insensible water loss”. That means if she losing 1 liter of water to sweat, respiration and feces per day plus 1 liter of water to urine (because she needs to dissolve her solute in something!), for her blood to stay the same osmolality, she must replace the water she lost thus must, at minimum, drink 2 liters of water per day.

jean_young2019  great explanation!Thank you!
... beeip made a comment on nbme21/block4/q#34 (A healthy 8-year-old boy is brought to the physician...)
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submitted by beeip(66)

"Excitatory amino acids" refers to glutamate, while "Biogenic" apparently refers to tyrosine, the precursor AA to dopamine and norepi.

sahusema  Amphetamines use the NE transporter (NET) to enter the presynaptic terminal, where they utilize the vesicular monoamine transporter (VMAT) to enter neurosecretory vesicles. This displaces NE from the vesicles. Once NE reaches a concentration threshold within the presynaptic terminal, the action of NET is reversed, and NE is expelled into the synaptic cleft
... hungrybox made a comment on nbme21/block4/q#20 (A 7-month-old boy is brought to the physician 2 days...)
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submitted by hungrybox(250)

This video explains genital embryology extremely well.

If you felt totally lost like me, watch the video first at 2x, then check out the bottom figure on pg. 608 in FA 2019.

Relevant to this question:

  1. SRY proteins stimulate development of testes
  2. This pt has testes => he must have the SRY gene on the Y chromosome
  3. MIF degrades the Mullerian duct, which would otherwise become the internal female genitalia
  4. This pt has internal female genitalia => didn't make enough MIF

Quiz yourself (answers in a separate post):

  1. This patient's disorder can be traced back to which cells?
  2. This patient had normal genitalia. If this patient had smaller genitalia than normal, that would be a defect in what enzyme?
ergogenic22  I like to work backwards. 1) patient has normal testicles on histology, normal appearing penis this must mean a Y chromosome is present, as testis determining factor is on the y chromosome (see above post point #2). I.e. you can eliminate choice A and B. Theoretically, 47XY and 47XYY could also present with female genitalia due to lack of MIF, but normal 46XY is more common
... hayayah made a comment on nbme21/block2/q#50 (A 65-year-old woman comes to the emergency...)
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submitted by hayayah(422)

Catheter placement:

https://aneskey.com/wp-content/uploads/2016/08/image00804.jpeg

Recall that the lung apex extends above the first rib.

hungrybox  His expression is so blissful. U can tell they're shootin up some full u-opioid agonist codeine type of shit and not some shitty partial u-opioid agonist buprenorphine type of shit or some shit like loperamide that doesn't even act on the CNS
rerdwins  even better, if you recall that the esophagus is RETROperitoneal ( its in like half the answer choices). hence, to get to it you have to go WAAYYYYY deep ( like rick and morty smuggling shit). after that, the lung option makes the most sense.
hello  Also, pulmonary artery is way too far away to be damaged by internal jugular vein catherization.
... cantaloupe5 made a comment on nbme21/block1/q#3 (An investigator is studying the efficacy of distinct...)
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submitted by cantaloupe5(38)

Capsular polysaccharide vaccines are often conjugated to proteins to improve immunogenicity. Flagellin is the only answer choice that's a protein.

... beeip made a comment on nbme21/block3/q#4 (A clinical trial is conducted to compare the...)
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submitted by beeip(66)

I might be the only person on earth who got this one wrong, but regardless:

"ITT analysis includes every subject who is randomized according to randomized treatment assignment. It ignores noncompliance, protocol deviations, withdrawal, and anything that happens after randomization."[1]

yo  You're not. I also goofed.
seagull  https://www.youtube.com/watch?v=Kps3VzbykFQ This video is a pretty decent explination worth your time on the subject.
hungrybox  I got it right but I was only like 50% sure. So I appreciate it.
... hungrybox made a comment on nbme21/block3/q#15 (A 47-year-old man has jaundice. Laboratory findings...)
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submitted by hungrybox(250)

why hemolysis is wrong:

There should almost never be straight up bilirubin in the urine. In hemolysis, the excess bilirubin is excreted in the bile. After bacterial conversion and reuptake, some will be excreted in the urine as urobilin. However, in obstructive disorders, the conjugated bilirubin will never have the opportunity to undergo bacterial conversion to sterco/urobilin. In this way, the conjugated bilirubin has no other way to be excreted other than directly in the urine.

credits to /u/alacran763 on reddit

... acanthosisnegrocans made a comment on nbme21/block2/q#40 (Acetaminophen and nonsteroidal antiinflammatory...)
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submitted by acanthosisnegrocans(10)

In the great words of Dr Sattar:

"Prostaglandin E2 mediates feeeeeeeeeever"

NSAIDs --> block prostaglandin syn

thisisfine   This is all I heard in my head
temmy  Me it was so weird
... seagull made a comment on nbme21/block1/q#2 (A 6-month-old girl is brought to the physician...)
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submitted by seagull(446)

! I hate these with a burning F***ing passion. Thumbs up if you agree

mcl  Amen brother
praderwilli  Every morning: "I think i'll go over glycogen storage diseases, lysosomal storage diseases, and dyslipidemias after questions this afternoon." Every afternoon: Nah
mcl  oh my god are you me
praderwilli  I recently found a program called Pixorize. It's pretty much Sketchy for biochem. Wish I discovered it sooner cuz it has helped for a lot of the painful things like this!
tentorium  [special]
tentorium  [special]
tentorium  [special]
drhello  hello
burak  Cherry red spot basically means niemann-pick or tay sachs. Two differences between is: 1- No HSM in Tay Sachs, HSM in niemann-pick. 2- Both of them has muscle weakness but there is hyperreflexia in Tay Sachs, but areflexia in niemann pick disease. In stem cell HSM is not described and hyperreflexia noted.
abhishek021196  What is HSM?
... rocmed made a comment on nbme21/block3/q#15 (A 47-year-old man has jaundice. Laboratory findings...)
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submitted by rocmed(0)

Patient has positive urine bilirubin test indicating that he has water soluble bilirubin accumulating in his body that has already been metabolized by UDP-glucuronosyltransferase. In order for water soluble bilirubin to be accumulating in his body there must be defective excretion of such bilirubin. The only option available that matches such is "obstruction of the bile duct".

... usmleuser007 made a comment on nbme21/block4/q#43 (A 4-year-old boy falls and lacerates his lower leg...)
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submitted by usmleuser007(131)
  1. Hemostasis (blood clotting): Within the first few minutes of injury,
    1. platelets in the blood begin to stick to the injured site.
    2. This activates the platelets, causing a few things to happen.
    3. They change into an amorphous shape, more suitable for clotting, and they release chemical signals to promote clotting.
    4. This results in the activation of fibrin, which forms a mesh and acts as "glue" to bind platelets to each other.
    5. This makes a clot that serves to plug the break in the blood vessel, slowing/preventing further bleeding.[5][6]

  2. Inflammation: During this phase, damaged and dead cells are cleared out, along with bacteria and other pathogens or debris.
    1. This happens through the process of phagocytosis, where white blood cells "eat" debris by engulfing it. 
    2. Platelet-derived growth factors are released into the wound that cause the migration and division of cells during the proliferative phase.

  3. Proliferation (growth of new tissue): In this phase, angiogenesis, collagen deposition, granulation tissue formation, epithelialization, and wound contraction occur.
    1. In angiogenesis, vascular endothelial cells form new blood vessels.
    2. In fibroplasia and granulation tissue formation, fibroblasts grow and form a new, provisional extracellular matrix (ECM) by excreting collagen and fibronectin.
    3. Concurrently, re-epithelialization of the epidermis occurs, in which epithelial cells proliferate and 'crawl' atop the wound bed, providing cover for the new tissue.
    4. In wound contraction, myofibroblasts decrease the size of the wound by gripping the wound edges and contracting using a mechanism that resembles that in smooth muscle cells.
    5. When the cells' roles are close to complete, unneeded cells undergo apoptosis.
  4. Maturation (remodeling): During maturation and remodeling,

    1. collagen is realigned along tension lines, and cells that are no longer needed are removed by programmed cell death, or apoptosis.

  5. Approximate times of the different phases of wound healing,[10] with faded intervals marking substantial variation, depending mainly on wound size and healing conditions, but image does not include major impairments that cause chronic wounds.
... hayayah made a comment on nbme21/block2/q#26 (A healthy 32-year-old woman at 35 weeks' gestation...)
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submitted by hayayah(422)

Stretch or dilation of the cervix and vagina are strong stimuli for oxytocin secretion, mediated by neural pathways called the Ferguson reflex.

Article: https://www.sciencedirect.com/topics/neuroscience/ferguson-reflex

... yo made a comment on nbme21/block3/q#45 (A 28-year-old man comes to the physician for...)
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submitted by yo(26)

I just knew that sperm need fructose, not sure what disease process this is though. He was pretty normal so 5a reducatase doesn't present like that. I wasn't sure if there was any odd use of the other answers. here is a link. Feel free to expand.

https://www.labce.com/spg27422_question.aspx

Fructose makes up 99% of the reducing sugar present in semen. This sugar is produced in the seminal vesicles. Diminished levels of fructose have been shown to parallel androgen deficiency and the testosterone level. Following testosterone therapy, the level of fructose increases. Although the fructose test is not part of a routine semen analysis, it is useful in cases of azoospermia (absence of sperm in semen). In azoospermia secondary to the absence of vesicles or if there is an obstruction, no fructose is present. In testicular azoospermia, fructose is present. When azoospermia and low semen volume exists, the fructose test should also be done, on a postejaculate urine sample to check for retrograde ejaculation. This occurs when the ejaculate goes into the bladder instead of out the urethra. The procedure for determining the amount of fructose in semen involves heating semen in a strong acid in the presence of resorcinol. Fructose gives a red color (Selivonoff reaction) and may be read in a photometer. The normal average is 315mg/dL fructose.

sam.l  Thank you for the explanation. I'm still confused about this answer. I was in between Zinc and fructose. Zinc deficiency also presents with anosmia (pg 71 First Aid 2019). Fructose is used for the movement. His hormones are normal.
d_holles  Apparently diabetes, occlusion, and inflammation can result in ↓ fructose in sperm. Mauss et al, Fert Stert 25, 1974 https://www.fertstert.org/article/S0015-0282(16)40391-2/pdf
cienfuegos  Thanks all for the info, quick note on the Zinc reply above @Sam.I: anosmia = lost sense of smell.
sam1  Great find yo! I believe this question was alluding to cystic fibrosis and the congenital absence of the vas deferens. Here is a link to a NEJM article about it below: https://www.nejm.org/doi/full/10.1056/NEJM196807112790203
burak  zinc deficiency cause hypogonadism. there is no hypogonadism, sperms are damaged?
... haliburton made a comment on nbme21/block2/q#2 (A 4-year-old girl is conscious but unable to breathe...)
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submitted by haliburton(87)

https://ghr.nlm.nih.gov/condition/pseudocholinesterase-deficiency

"People with pseudocholinesterase deficiency may not be able to move or breathe on their own for a few hours after [fast-acting drugs, such as succinylcholine and mivacurium] are administered.

ragacha  THX
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