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NBME 23 Answers

nbme23/Block 1/Question#32

Which of the following sets of serum findings is ...

Phosphate: increased;
Ca2+: decreased;
Parathyroid hormone: increased


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 +1  upvote downvote
submitted by imnotarobotbut(23),

Secondary hyperparathyroidism due to chronic renal failure. Low Ca, high phosphate and high PTH. FA 2019 page 342

imnotarobotbut  Basically PTH keeps telling the kidney that it wants it to reabsorb Calcium and dump phosphate, but the kidney is broken and cant do that. +  




 +1  upvote downvote
submitted by mguan1993(2),

Does being recently diagnosed vs having CKD for a while change this answer? the "recently diagnosed" part threw me off

smc213  @mguan1993 yes it does! With secondary hyperPTH due to CKD = incr. phosphate, dec. Ca2+ and incr. PTH. This can then progress to tertiary hyperPTH from longstanding secondary hyperPTH as a result of parathyroid HYPERPLASIA --> autonomously (refractory) functioning parathyroid. This will actually lead to INCREASED Ca2+, and significantly INCREASED PTH. Treatment would be surgical removal of the parathyroid glands. Sources: DIT and FA18 p340 +1  




 +0  upvote downvote
submitted by dentist(2),

I took the simplistic approach: I chose the opposite of whatever the kidney usually does and then lack of neg PTH feedback