Where is the thyroid?

How does the thyroid work?

The thyroid forms three in total:

  • Triiodothyronine or T3
  • Tetraiodothyronine or T4
  • Calcitonin

Strictly speaking, only T3 and T4 are counted among the actual thyroid hormones. They are made in the so-called follicular epithelial cells of the thyroid gland.

An important part of both is iodine. The body cannot produce the trace element iodine itself; it has to take it in regularly with food. The iodine reaches the blood via the intestine and into the thyroid gland, where it is incorporated into the thyroid hormones after several intermediate steps.

The body sometimes needs more, sometimes less thyroid hormones. In order to be able to adapt the hormone production exactly to the demand, the thyroid gland needs support from another gland: the pituitary gland (pituitary gland). It regulates how much hormone is released from the thyroid into the blood. In the blood, thyroid hormones are also bound to a certain extent to transport proteins. If the body needs more, bound T3 and T4 in the blood are split off from the proteins and can then take effect.

The third hormone made in the thyroid is calcitonin. Calcitonin is produced by so-called C cells and is involved in calcium and bone metabolism.

T3 and T4 increase the body's basal metabolic rate. Under their influence, all body cells work more intensively and thus consume more energy. The consequences are, for example:

  • Increase in body temperature
  • fast pulse and strong heartbeat
  • rapid utilization of food by reducing the energy reserves in the liver and muscles
  • Promotion of brain maturation (in children)
  • Promotion of growth (in children)
  • high alertness and quick reflexes due to increased activity of the nervous system