Pre- and post-operative hypothalamic-pituitary-thyroidal axis function in patients with prolactinoma, growth hormone...

Pre- and postoperative hypothalamic-pituitary-thyroid axis function was studied in 38 patients with pituitary adenomas (PRL, GH and ACTH tumours), of whom 35 were surgically confirmed and three diagnosed by clinical signs, CT scanning and hormone assessments. About ten days after operation, the same study was repeated in 10 patients with prolactinoma and 7 with growth hormone (GH) tumour. The preoperative abnormal serum TSH response to TRH was found in 8/20 patients with prolactinoma, 9/16 with GH tumour, and 2/2 with Cushing's disease due to ACTH microadenoma. The incidence of abnormal TSH response to TRH was not significantly increased in patients with larger adenoma in either PRL or GH tumour group. In 8 cases of prolactinoma, metoclopramide (MCP, 10 mg, P.O.) test was also performed and there was a significant positive correlation between TSH responses to TRH and to MCP. Serum TT3 in the GH tumour group was within normal ranges, but significantly higher than that of the normal and prolactinoma groups. After operation, TT3 was significantly decreased as compared with that before operation and there were marked changes in TSH response to TRH. In conclusion, there were some abnormalities in TSH control in patients with non-TSH pituitary tumour, and in serum TT3 control in patients with GH tumour. The surgical treatment of pituitary adenoma can lead to transient decrease in TSH reserve and serum TT3 level probably resulting from both stress and/or destruction of thyro-trophs by the operation.