Hyperthyroidism and acromegaly due to a thyrotropin- and growth hormone-secreting pituitary tumor. Lack of hormonal response to bromocriptine.

A 47-year-old woman with acromegaly and hyperthyroidism was found to have an inappropriately normal serum thyrotropin level (1.5 to 2.5 microU/ml) that responded poorly to thyrotropin-releasing hormone but showed partial responsiveness to changes in circulating thyroid hormones. Serum alpha-subunit levels were high-normal and showed a normal response to thyrotropin-releasing hormone. Growth hormone and thyrotropin hypersecretion persisted despite radiotherapy and bromocriptine treatment. Selective trans-sphenoidal removal of a pituitary adenoma led to normalization of both growth hormone and thyrotropin levels. Both thyrotropes and somatotropes were demonstrated in the adenoma by the immunoperoxidase technique and electron microscopy.