hypothyroidism

Deficient functioning of the thyroid gland, causing slowed mental and physical performance, weight gain, sensitivity to cold, and susceptibility to infection.

This may be due to lack of iodine in the diet or a defect of the thyroid gland, both being productive of goitre; or to the pituitary gland providing insufficient stimulus to the thyroid gland. Treatment of thyroid deficiency is by the hormone thyroxine. When present from birth, hypothyroidism can lead to cretinism if untreated.