I think what threw me off with this question was "serum T4" - wasn't sure if that meant total T4 or serum T4. Luckily, I don't think any of the other ones fit for either so I assumed it meant total T4 for which the answer makes sense
"Increased blood concentrations of T4-binding globulin: TBG is one of several proteins that transport thyroid hormones in blood, and has the highest affinity for T4 (thyroxine) of the group. Estrogens stimulate expression of TBG in liver, and the normal rise in estrogen during pregnancy induces roughly a doubling in serum TBG concentratrations."
"Increased levels of TBG lead to lowered free T4 concentrations, which results in elevated TSH secretion by the pituitary and, consequently, enhanced production and secretion of thyroid hormones. The net effect of elevated TBG synthesis is to force a new equilibrium between free and bound thyroid hormones and thus a significant increase in total T4 and T3 levels. The increased demand for thyroid hormones is reached by about 20 weeks of gestation and persists until term."
http://www.vivo.colostate.edu/hbooks/pathphys/endocrine/thyroid/thyroid_preg.html
Struma ovarii is a type of teratoma that produces thyroid hormone. However, due to the negative fb, TSH levels would be extremely low.
Similarly, Graves would have low TSH.
Placenta delivers T4 to fetus, not the other way around. Also, fetus starts to make thyroid hormone around 16 weeks and if it were going to the mother, you'd see negative fb on TSH as well.
TSH producing pituitary tumor would have a high TSH.
Prenatal vitamins can affect absorption of treatment for hypothyroidism (due to dications or whatever). They do not contain T4 because that just doesn't make sense lol
Goljian: Pregnancy/ OCP use: High T4, normal TSH Steroids(anabolic): Low T4, normal TSH
submitted by โdrmohandes(193)