Summary
The thyroid gland produces two important thyroid hormones, the biologically largely ineffective thyroxine (T4) and the effective triiodothyronine (T3). They are synthesized in the thyroid cells with the help of iodine and are released from the thyroid follicles as required. The effective T3 is released directly from the thyroid gland in much lower concentrations, but is produced from T4 by the mechanism of deodorization.
This prevents the immediate effect of T3 and the individual organs can control the conversion and thus the effect themselves.The entire release and production of thyroid hormones is controlled by hormones from the hypothalamus and pituitary gland, which in turn are regulated by the current concentration in the blood. This principle is called negative feedback and is necessary to control the concentration of hormones in the blood. The inactivation of the effective T3 takes place in the liver and kidney.
However, the thyroid gland can also release too much or too little hormone. This is called hyperthyroidism or hypothyroidism and can be treated well in most cases and depending on the cause.
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