Bromocriptine therapy for hyperthyroidism due to increased thyrotropin secretion.

ABSTRACT

We describe a patient with TSH-induced hyperthyroidism successfully treated with bromocriptine. A 25-yr-old woman was found to have hyperthyroidism due to excessive TSH secretion; no pituitary tumor was found. Her serum T4 level ranged between 21.9 and 25.9 micrograms/dl and that of T3 between 283 and 314 ng/dl. Serum TSH was between 5 and 9 microU/ml with an exaggerated response to TRH. Basal metabolic rate was +26 to +38%. Serum PRL was also elevated (79 ng/ml). Administration of bromocriptine for 4 months decreased serum TSH and PRL levels to normal with a concomitant fall in levels of serum T3 and T4. Regression of the clinical manifestations of hyperthyroidism occurred during bromocriptine drug therapy. These results suggest that reduction in hypothalamic dopaminergic tone may have contributed to the inappropriately increased TSH secretion in the patient.