Thyroxine (T4)
A) is formed by coupling one MIT and one DIT within the colloid.
B) is produced by the C cells of the thyroid gland.
C) exerts a calorigenic effect.
D) inhibits thyroid-stimulating immunoglobulin in negative-feedback fashion.
E) is more potent than tri-iodothyronine.

Question

Quizplus · Accepted Answer

Thyroxine (T4) exerts a calorigenic effect by increasing oxygen consumption and heat production in the body. This helps to maintain body temperature and metabolic rate.

Answer: A
 Thyroxine (T4) is formed by coupling one molecule of monoiodotyrosine (MIT) and one molecule of diiodotyrosine (DIT) within the colloid of the thyroid follicles.

Answer: D
 Thyroxine (T4) does not inhibit thyroid-stimulating immunoglobulin (TSI) in negative-feedback fashion. Instead, TSI stimulates the thyroid gland to produce more T4 and tri-iodothyronine (T3).

Answer: E
 Tri-iodothyronine (T3) is more potent than thyroxine (T4) because T3 has fewer iodine atoms attached to the thyronine ring, making it more biologically active.