Question

Low levels of TSH can be found in

• A. Cretinism
• B. Hyperthyroidism
• C. Hypothyroidism
• D. Jet lag

Answer 1

The correct option is B Hyperthyroidism

TSH or thyroid stimulating hormone is secreted by the anterior pituitary. TSH stimulates the thyroid gland to release the thyroid hormones triiodothyronine ($T_3$) and thyroxine ($T_4$). When the $T_3$ and the $T_4$ levels get too high, they exert a negative feedback on the hypothalamus and the anterior pituitary, so less TSH is secreted. In hyperthyroidism, $T_3$ and $T_4$ levels are abnormally high, so they inhibit the secretion of TSH, bringing down its levels.

In both cretinism and hypothyroidism, there is an abnormally low secretion of the thyroid hormones, so the TSH levels are higher than usual.

Jet lag is a condition that results from travel between different time zones, when the body clock takes time to adjust to the new time zone.