Definition
The abbreviation TSH is the so-called “thyroid-stimulating hormone”, or “thyrotropin”. It consists of amino acids, which are chained together as a protein. For this reason it is also called peptide hormone.
TSH is secreted from the pituitary gland (hypophysis). The corresponding hormone, which in turn activates the pituitary gland to produce TSH, is called “TRH”, or “thyrotropin-releasing hormone”. This name already contains the function, it serves the formation/release of “thyrotropin”, i.e. TSH.
From the pituitary gland, the TSH then reaches the thyroid gland via the blood. There it binds to the TSH receptor and increases the iodine uptake into the thyroid, the formation and release of thyroid hormones and the growth of the thyroid gland. Sufficient iodine uptake into the thyroid gland is important, as iodine is an important component of thyroid hormones. Thyroid hormones increase the metabolism and affect almost all organs and tissues in the body.
Function of TSH
After the effect of TRH on the pituitary gland, TSH is released. This is released into the blood and has the thyroid gland as its target organ. Here the TSH causes the release of the thyroid hormones T3 (triiodothyronine) and T4 (thyroxine), which are essential for survival.
This finely regulated cycle is known as the thyrotropic control circuit. This control circuit ensures a balance of the thyroid hormones T3 and T4 in the blood and guarantees proper bodily function. The thyroid hormones that are now released cause, for example, an increase in the heart rate in the heart, a stronger blood supply to the lungs and an increased build-up of muscle fibers in the skeleton.
In the metabolism, they cause an increased basal metabolic rate due to increased oxygen consumption and a higher body temperature. Crucial systems of the body are controlled by this regulatory circuit “interbrain-pituitary-thyroid axis” (hypothalamus-hypohysis axis), which requires a sensitive feedback to the exact amount needed. Here, the circulating hormones of the respective organs partly act on their upstream organ and inhibit here, at increased concentration, the release of their activating hormone.
T3 and T4, for example, inhibit the release of TSH but also inhibit the release of TRH at a higher level (so-called negative feedback). TSH is also inhibited by other important hormones such as cortisone or dopamine. Briefly summarized: TSH acts on the release of thyroid hormones and thus controls their function.
All articles in this series:
