Pituitary enlargement, pituitary failure, and primary hypothyroidism

Enlargement of the pituitary gland associated with primary hypothyroidism was observed in two patients. Serum thyroid-stimulating hormone (TSH) concentration and the TSH response to thyrotropin-releasing hormone were increased in both. Other pituitary function tests were subnormal in both patients, suggesting that a thyrotroph pituitary tumor was present that compromised the other pituicytes. The presence of a pituitary tumor secondary to primary hypothyroidism and resulting pituitary failure should be considered in all patients with long-standing primary hypothyroidism.