Undersupply of the organism with the thyroid hormones triiodothyronine (T3) and thyroxine (T4) and a resulting state of hypometabolism. In most cases an underfunction of the thyroid gland (primary hypothyroidism) is responsible for the hypometabolism. Very rare are the pituitary or hypothalamic disorders of secondary or tertiary hypothyroidism.
The resulting hormone deficiency slows down numerous metabolic functions of the body. The consequences are reduced physical and mental performance. The diagnosis of florid hypothyroidism is obvious. In less pronounced hypothyroidism (e.g. hypothyroidism in the elderly), an uncharacteristic symptom pattern is in the foreground; in some cases symptoms may be completely absent.