Thyroid gland, disorders of

Disorders of the thyroid gland may cause hyperthyroidism, hypothyroidism, or enlargement or distortion of the gland. Myxoedema, Graves’ disease, and Hashimoto’s thyroiditis are common disorders. Goitre may sometimes occur with no accompanying abnormality of thyroid function. In rare cases, the gland is absent at birth, producing severe cretinism. Sometimes it develops in an abnormal position in the neck, causing, in rare cases, difficulty in swallowing or breathing. A genetic disorder may impair the thyroid’s ability to secrete hormones and goitre may result. Thyroid infection is uncommon and leads to thyroiditis. Viral infection can cause extreme pain and temporary hyperthyroidism. Hormonal changes during puberty or pregnancy may cause a degree of goitre temporarily. Hyperthyroidism due to excessive production of TSH by the pituitary gland is rare but can occur as a result of a pituitary tumour. Because iodine is necessary for the production of thyroid hormone, its deficiency may lead to goitre. Severe iodine deficiency in children may cause myxoedema. (See also thyroid cancer.)