What is the primary function of thyroid-stimulating hormone (TSH)?

The primary function of thyroid-stimulating hormone (TSH) is to stimulate the thyroid gland to produce thyroid hormones, predominantly thyroxine (T4) and triiodothyronine (T3). TSH is synthesized and secreted by the anterior pituitary gland in response to thyrotropin-releasing hormone (TRH) from the hypothalamus. Once released, TSH binds to specific receptors on the thyroid gland, promoting the uptake of iodine and the synthesis of thyroid hormones.

These thyroid hormones play a crucial role in regulating metabolism, growth, and development, affecting almost every cell in the body. The production of TSH is regulated through a feedback mechanism involving the levels of thyroid hormones in the bloodstream; as T4 and T3 levels rise, TSH production decreases, maintaining hormonal balance within the body.

In contrast, the other answer options address functions that are not related to TSH. Regulating calcium levels is primarily related to parathyroid hormone (PTH) and calcitonin, inhibiting hormone production does not pertain to TSH's role, and increasing heart rate is mainly influenced by other hormones such as adrenaline, rather than TSH.