SERUM LEVELS OF FSH AND TSH IN NONFUNCTIONING PITUITARY ADENOMAS BEFORE AND AFTER SURGERY

Clinically nonfunctioning human pituitary adenomas (NFPAs) constitute about 25-35% of pituitary tumours. Relatively few studies have been carried out to determine the cellular origin and biology of the NFPAs. The present study was undertaken to assess the effect of surgical removal of adenoma on peripheral adenohypophyseal hormones. In addition, the pituitary hor- mones have also been measured directly in the adenoma tissue following its surgical removal. The present study is based on 19 patients (16 males and 3 females), 30-50 year of age, diagnosed for NFPAs on the basis of clinical and radiological evidence. Follicle stimulating hormone (FSH) and thyroid stimulating hormone (TSH) were determined in serum before and following trans- sphenoidal adenomectomy. The FSH, TSH content of the excised adenoma tissue was also mea- sured in male patients. The results demonstrate that in a subset of 4 of the 16 male patients with NFPAs the presurgical serum FSH values (45.1±0.7 mIU/ml) were markedly and significantly greater than those of the remaining 12 patients (7.9±0.7 mIU/ml) and of control subjects (8.8±0.6 mIU/ml). Following removal of the adenoma in these 4 patients, peripheral serum FSH levels fell within the normal range. In the remaining 12 patients peripheral and mean FSH levels were within the normal range. Following removal of the adenoma in 2 female patients, serum FSH concentrations showed a marked decline of FSH levels (5.7 mIU/ml and 7.2 mIU/ ml) whereas in the remaining one patient, the FSH levels remained relatively high (34.5 mIU/ ml). The adenoma tissue FSH content in patients with initial higher serum FSH levels, was also significantly greater than that of the other patients (21.5±2.1 vs 4.4±1.9 IU/g). The presurgical mean serum TSH concentrations in patients with NFPA were mostly in the lower normal range and were not significantly different from the control (1.0±0.2 vs 1.5±0.4 :IU/ml) and removal of the adenoma did not affect the serum TSH levels significantly. The TSH content of adenoma tissue was either non-detectable or in the low range as compared to the TSH content determined in control pooled pituitary tissue. The present study suggests that pituitary tumours diagnosed as NFPAs constitute a heterogenous group of adenomas with regard to their secretory activity of intact adenohypophyseal hormones. Whereas some of these adenomas activity may syn- thesize one or more pituitary hormones, peripheral concentrations may not be sufficient to pro- duce overt clinical symptoms of hormone hypersecretion.