Pituitary enlargement and primary hypothyroidism: a report of two cases with sharply contrasting outcomes.

Primary hypothyroidism may be associated with pituitary enlargement. Two cases of pituitary enlargement with suprasellar extension associated with primary hypothyroidism are presented. In one patient, prompt regression of the pituitary enlargement occurred with replacement doses of L-thyroxine. In the second patient, there was progressive enlargement of the pituitary gland while the patient was on L-thyroxine therapy with documented normalization of serum levels of thyroid-stimulating hormone. We recommend repeat evaluation of all patients with pituitary enlargement that is thought to be secondary to primary hypothyroidism to document regression of pituitary size after L-thyroxine therapy.