Thyrotropin-secreting pituitary adenoma

Thyrotropin (TSH)-secreting pituitary adenoma (TSPA) is a rare cause of hyp erthyroidism and detailed reports of this entity in Taiwan are uncommon. We report a patient with TSPA with symptoms of hyperthyroidism and describe t he presentation, endocrine and histologic findings, and treatment. The pati ent, a 42-year-old man, presented with a 2-year history of weight loss, pal pitation, anxiety, and bad temper. He had increased basal serum thyroxine ( T-4, 18.3 mu g/dL) and triiodothyronine (T-3, 250 ng/dL) concentrations. Th e TSH concentration was normal (4.6 mu IU/mL) and showed impaired response to stimulation by TSH-releasing hormone. Tests for antithyroid antibodies w ere negative. Thyroid scintigraphy showed mild thyroid enlargement. The thy roid uptake of radioactive iodine (I-131) was high at 2 hours (34%) and 24 hours (63%) after I-131 administration. Other serum hormone concentrations mere within normal limits. Magnetic resonance imaging of the brain showed a microadenoma in the pituitary region. Octreotide and bromocriptine tests s howed 78.4% and 58.3% inhibition of TSH, respectively. The patient underwen t trans-sphenoidal pituitary tumor excision, and the symptoms of hyperthyro idism subsided after surgery. Six months after the operation, there was no evidence of recurrence of the tumor or symptoms of hyperthyroidism. Hormona l supplements were also not necessary. In conclusion, TSPA is a rare cause of hyperthyroidism. However, in patients with symptoms of hyperthyroidism a nd increased basal serum T-4 and T-3 concentrations, but normal or even ele vated serum TSH concentrations, TPSA should be considered in the differenti al diagnosis.