RELATIVE SPARING OF ANTERIOR-PITUITARY FUNCTION IN PATIENTS WITH GROWTH HORMONE-SECRETING MACROADENOMAS - COMPARISON WITH NONFUNCTIONING MACROADENOMAS

Pre- and postoperative anterior pituitary function was assessed in 26 subjects with nonfunctioning macroadenoma (NFMA) and in 15 acromegalic subjects with macroadenomas. Preoperatively, NFMA patients had a high er prevalence of secondary hypogonadism (78% vs. 40%; P < 0.05), hypot hyroidism (23% vs. 0%; P = 0.06), and hypoadrenalism (43% vs. 7%; P = 0.02) compared to individuals with GH-secreting macroadenoma (GHMA). P atients with NFMA also had a higher prevalence of more severe pituitar y failure compared with acromegalic patients; 56% of the patients in t his group had more than one pituitary hormone axis impaired compared t o only 8% in the acromegalic group. These differences could not be acc ounted for by tumor grade and/or stage. Transsphenoidal pituitary surg ery led to a significant improvement in anterior pituitary function in the NFMA group. Nevertheless, the prevalence of pituitary deficiency postoperatively was still significantly greater in NFMA patients than in the acromegalic group (68% us. 17%, respectively; P < 0.04). The re sults suggest that anterior pituitary function is better preserved in GHMA than in NFMA and that this difference is independent of tumor siz e. The mechanism underlying the lower rate of hypopituitarism in acrom egalics with macroadenomas remains to be elucidated.