Normalization of thyroid stimulating hormone levels in acromegalic patients after selective adenomectomy

Changes in TSH secretion in six acromegalic patients were studied before and after transsphenoidal adenomectomy (Hardy's method) and compared to normal subjects and six patients with prolactinoma. Basal serum GH levels ranging from 5 to over 250 ng/ml before adenomectomy decreased to below 5 ng/ml after the operation, and the abnormal responses of GH to TRH observed initially in three of the six patients almost disappeared in the post-adenomectomy period. The response of serum TSH to TRH in acromegalic patients improved in each of the six patients after the operation. The TRH-stimulated TSH secretion in patients with prolactinoma of a size and grade similar to those in acromegalic patients was not so extremely low as that in the acromegalic subjects. As indicators of thyroid function, serum triiodothyronine (T3), thyroxine (T4), T3-uptake levels and free T4 indices did not change significantly after adenomectomy as compared with those before the operation in five of the six patients tested. Serum T3, T4 and T3-uptake levels and free T4 indices before adenomectomy were normal or subnormal in each patient except for a high serum T4 level and free T4 index before the operation in only one patient. Thus, it is difficult to conclude that the function of thyrotrophs was decreased by pressure upon the intact pituitary gland by the tumor, or that the thyroid gland also became hypertrophic secondary to the elevated GH, resulting in a large quantity of thyroid hormone being secreted, which caused a suppression of TSH secretion by negative feedback.(ABSTRACT TRUNCATED AT 250 WORDS)