Thyroid-stimulating hormone (TSH) is a glycoprotein that is synthesized in the anterior pituitary gland. It is the main regulator of the thyroid gland, as it affects the production of thyroid hormones (T3 and T4).

How does it work?

• Control by the hypothalamus: TSH production is regulated by thyrotropin-releasing hormone (TRH) secreted by the hypothalamus.
• Thyroid hormone feedback: If blood levels of T3 and T4 decrease, TSH increases, stimulating the thyroid gland to produce more hormones. If T3 and T4 levels increase, TSH decreases.