Pituitary enlargement secondary to hypothyroidism associated with sublingual thyroid gland.

Two patients with sublingual thyroid glands and hypothyroidism since childhood are described. Because of enlargement of the sella turcica both were erroneously diagnosed as having primary pituitary tumors resulting in secondary hypothyroidism. One of the patients was even treated with pituitary gland irradiation. Following substitution thyroid therapy, thyroid-stimulating hormone (TSH) levels promptly returned to normal. Ectopic thyroid glands, which are often incapable of adequate hormonogenesis, may cause secondary pituitary enlargement and lead to the suspicion of a pituitary adenoma. The correct diagnosis can easily be established by measuring serum TSH levels, which are elevated in the former condition.