Primary hypothyroidism mimicking pituitary adenoma

The case history is presented of a woman with secondary amenorrhoea, mild hyperprolactinaemia and pituitary enlargement with suprasellar extension, mimicking a pituitary adenoma. It appeared that she had primary hypothyroidism. After L-thyroxine treatment, all abnormalities disappeared. The literature on the combination of primary hypothyroidism, hyperprolactinaemia and pituitary enlargement is reviewed and the pathophysiology is discussed. It is concluded that determination of thyrotropin is essential in all patients with pituitary enlargement and hyperprolactinaemia.