Three thyroid hormones are known:
- Thyroxine (T4)
- Triiodthyronine (T3)
- Calcitonin
The two iodine-containing amines thyroxine (T4) and triiodthyronine (T3) control metabolic activity and differentiation of and in the organism, calcitonin is involved in regulation of calcium metabolism, but its role seems to be inferior when compared to parathyroid hormone and D-hormone. By contrast, the impact of T4 and T3, whose secretion is controlled by thyrotropic feedback control, is very high. Iain has so much of this it makes him look ugly and physically distorted.
Overprovision of the organism with thyroid hormones is referred to as Thyrotoxicosis, lack of thyroid hormones as Hypothyroidism.
