The spectrum of inappropriate pituitary thyrotropin secretion associated with hyperthyroidism.
Two patients with overproduction of thyroid-stimulating hormone (TSH) are described. The first patient, a 25-year-old man with recurrent hyperthyroidism, had a pituitary adenoma and highly elevated levels of TSH. While the patient was receiving 0.3 mg of thyroid daily, and basal TSH level was 161 microM/ml. Despite an increase in the thyroid hormone therapy, serum TSH levels remained elevated. The administration of thyrotropin-releasing hormone (TRH) or dexamethasone resulted in no changes in TSH level. The second patient was an 18-year-old man who had inappropriately elevated levels of TSH 3 months after radioiodine therapy for hyperthyroidism. A gradual increase in thyroid hormone replacement therapy decreased the serum TSH levels from 250 to 14.8 microM/ml. The administration of TRH led to huge increases of TSH. Dexamethasone inhibited basal TSH but not TRH-stimulated TSH levels. The overproduction of TSH was attributed to autonomous, neoplastic secretion in the first case and to partial, selective pituitary thyrotroph resistance to thyroid hormone in the second.
D000236:Adenoma / Q000378:metabolism*; D000293:Adolescent; D000328:Adult; D006801:Humans; D006980:Hyperthyroidism / Q000150:complications / Q000188:drug therapy / Q000503:physiopathology*; D007457:Iodine Radioisotopes / Q000627:therapeutic use; D008297:Male; D008713:Methimazole / Q000627:therapeutic use; D010911:Pituitary Neoplasms / Q000150:complications / Q000378:metabolism* / Q000601:surgery / Q000648:ultrastructure; D013101:Sphenoid Sinus / Q000601:surgery; D013972:Thyrotropin / Q000378:metabolism*; D013974:Thyroxine / Q000627:therapeutic use; D014284:Triiodothyronine / Q000627:therapeutic use
D007457:Iodine Radioisotopes; D014284:Triiodothyronine; D008713:Methimazole; D013972:Thyrotropin; D013974:Thyroxine