Which of the following hormones does NOT belong to the thyroid hormones?

The hormone that does not belong to the thyroid hormones is thyrotropin. Thyrotropin, also known as thyroid-stimulating hormone (TSH), is produced by the anterior pituitary gland and plays a crucial role in regulating the production of thyroid hormones T3 (triiodothyronine) and T4 (thyroxine) from the thyroid gland.

T3 and T4 are indeed the primary hormones secreted by the thyroid gland and are directly involved in regulating metabolism, growth, and development within the body. The term "thyroid hormone" can refer generally to both T3 and T4, encompassing their function and importance. However, thyrotropin is not synthesized or secreted by the thyroid itself, making it distinctly separate from the hormones produced by that gland. Thus, T3, T4, and the category of thyroid hormones all originate from the thyroid gland, while thyrotropin originates from a different gland, reinforcing why it is the one that does not belong to the thyroid hormones.