The thyroid hormones, thyroxine (T4) and triiodothyronine (T3), are tyrosine-based hormones produced by the thyroid gland.
An important component in the synthesis is iodine.
The thyronines act on the body to increase the basal metabolic rate, affect protein synthesis and increase the body's sensitivity to catecholamines (such as adrenaline) by permissiveness.
The thyroid hormones are essential to proper development and differentiation of all cells of the human body.
These hormones also regulate protein, fat, and carbohydrate metabolism, affecting how human cells use energetic compounds.
Numerous physiological and pathological stimuli influence thyroid hormone synthesis.
The thyronamines function via some unknown mechanism to inhibit neuronal activity; this plays an important role in the hibernation cycles of mammals.
One effect of administering the thyronamines is a severe drop in body temperature.