TSH levels in blood are often used by doctors to adjust doses of thyroid hormone replacement medications such as Synthroid. Why is TSH a good indicator of circulating thyroid hormone levels?
A) because TSH is negatively regulated by thyroxine levels
B) because TSH is positively regulated by thyroxine levels
C) because TSH synthesis takes place in the cytoplasm of thyroid cells
D) because TSH controls the production and secretion of TRH

Question

Quizplus · Accepted Answer

TSH (thyroid stimulating hormone) is negatively regulated by thyroxine levels, meaning that when there are high levels of circulating thyroid hormone (thyroxine), TSH production is suppressed. Conversely, when there are low levels of circulating thyroid hormone, TSH production is stimulated. Therefore, measuring TSH levels can provide an indirect indication of thyroid hormone levels in circulation.

TSH Levels in Blood Are Often Used by Doctors to Adjust