[Hyperthyroidism caused by inadequate TSH secretion].

At 5 years of age inappropriate thyrotropin secretion was diagnosed in a girl now 11 years old. She had clinical signs of hyperthyroidism, and circulating thyroid hormones were elevated, but the TSH-level was within normal range. There was no evidence of a pituitary tumor. Therapy with bromocriptine, dexamethasone, and D-thyroxine had no measurable effect. The treatment with methimazole led to normal levels of circulating thyroid hormones, however, the TSH-level increased and the thyroid gland became diffusely enlarged. By the administration of 3,5,3'-triiodothyroacetic acid (TRIAC) (at present 20 micrograms/kg body weight) the TSH-level was lowered and a long-term remission of hyperthyroidism was achieved.