Thyroid-Stimulating Hormone (TSH)

Thyroid-stimulating hormone (TSH) is a hormone produced by the pituitary gland, which is located at the base of the brain. It plays a crucial role in the regulation of the thyroid gland, which is responsible for controlling the body's metabolism.

Function of TSH

TSH stimulates the thyroid gland to produce and release the hormones thyroxine (T4) and triiodothyronine (T3). These thyroid hormones are essential for regulating the body's metabolism, growth, and energy expenditure.

Regulation of TSH

The secretion of TSH is regulated by a feedback mechanism involving the hypothalamus, pituitary gland, and thyroid gland. When the levels of T4 and T3 in the blood are low, the hypothalamus releases thyrotropin-releasing hormone (TRH), which stimulates the pituitary gland to release TSH. In turn, TSH stimulates the thyroid gland to produce more T4 and T3. When the levels of T4 and T3 are high, the production of TSH is inhibited, leading to a decrease in thyroid hormone production.

Clinical Significance

Abnormal levels of TSH can indicate thyroid disorders. High levels of TSH may indicate an underactive thyroid (hypothyroidism), while low levels of TSH may indicate an overactive thyroid (hyperthyroidism). Testing TSH levels is a common diagnostic tool for thyroid conditions.

Study Guide

1. What is the function of thyroid-stimulating hormone (TSH)?
2. Describe the regulation of TSH secretion in the body.
3. What are the clinical implications of abnormal TSH levels?
4. How are TSH levels used in the diagnosis of thyroid disorders?