Which factors predict the results of pituitary surgery in acromegaly?

Abstract

Abstract. Thirty-one patients with acromegaly who underwent pituitary surgery were investigated for possible predictive factors of the surgical outcome. The patients were divided into two groups: those whose GH levels normalized (<5 μg/l) after operation, group A (N = 18), and those whose GH levels remained elevated, group B (N = 13). There were no differences in age, sex distribution and sellar volume between both groups. There was a tendency to a higher incidence of suprasellar extension of the pituitary tumor in group B (P < 0.10). The basal GH levels in group A (38 ± 5 μg/l) before operation were significantly lower than in group B (100 ± 22 μg/l, P < 0.002). Somatomedin C levels after the operation were significantly lower in group A than in group B (P < 0.05) and were more often in the normal range (P < 0.05). No differences were found in the occurrence of paradoxical GH responses to TRH and/or to GnRH between the groups and neither were there any differences in GH responses to GHRH and to bromocriptine between the groups. The sensitivity to SRIH tended to be higher in group A. After operation, the paradoxical GH response to TRH disappeared in 7 out of 10 patients and to GnRH in 2 out of 5 patients of group A, whereas in group B this anomaly persisted in all 9 after TRH and all 3 patients after GnRH. Hypopituitarism developed in only 5 out of the 31 patients. We conclude that the basal GH level is a factor that to a large extent may predict the effect of pituitary surgery in acromegaly. However, despite normalization of the basal GH level, paradoxical responses to TRH and or GnRH persist in a minority of the cured patients, indicating the presence of remnants of the pituitary adenoma.