The underproduction of thyroid hormones by an underactive thyroid gland. Most cases are caused by an autoimmune disorder such as Hashimoto’s thyroiditis. More rarely, hypothyroidism results from the removal of part of the thyroid gland to treat hyperthyroidism. Symptoms include tiredness and lethargy. There may also be muscle weakness, cramps, a slow heart-rate, dry skin, hair loss, a deep and husky voice, and weight gain. A syndrome called myxoedema, in which the skin and other tissues thicken, may develop. Enlargement of the thyroid gland may also occur (see goitre). If the condition occurs in childhood, it may retard growth and normal development. The disorder is diagnosed by measuring the level of thyroid hormones in the blood. Treatment consists of replacement therapy with the thyroid hormone thyroxine; usually for life.


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