Function of the thyroid gland

The thyroid gland produces the vital hormones “thyroxine” (T4) and “triiodothyronine” (T3).

These hormones are partly responsible for every metabolic activity in our body. This means that without thyroid hormones, proteins, fats and carbohydrates can only be metabolised to a limited extent.

To produce thyroid hormones, the thyroid gland needs iodine as a basic substance, which we must take in with our food. The necessary daily iodine requirement is 150-200 µg for adults, between 40 and 80 µg for infants and between 100 and 180 µg for children. When metabolic turnover is increased, e.g. during pregnancy, approx. 230 µg of iodine is required daily.

Because a balanced thyroid hormone level is vital for our body, hormone production in the thyroid gland is subject to precise control mechanisms. The level of the thyroid hormones T3 and T4 in the blood is continuously measured. The pituitary gland (“hypophysis”) produces the hormone TSH (thyroid-stimulating hormone), which stimulates hormone production in the thyroid gland. If too little thyroid hormone is produced, the TSH level rises, and vice versa.

In addition, TSH production in the pituitary gland is controlled and monitored by a further feedback loop. In the so-called “hypothalamus” (a part of the diencephalon), the hormone TRH (thyrotropin-releasing hormone) is produced, which monitors the control of TSH by the pituitary gland.

This double safeguard ensures that the thyroid hormone level is kept constant.