Growth hormone secretion in recently operated acromegalic patients

GH secretion patterns were studied in 14 recently transsphenoidally operated patients by measuring GH concentrations in blood sampled every 10 min over 24 h with a highly sensitive time-resolved immuno-fluorescent assay. Plasma GH concentrations were analyzed with a discrete peak detection program (Cluster) and a multiparameter deconvolution technique. Diurnal variations were analyzed by cosinor analysis. Nine or 10 days after pituitary surgery all patients had a normal plasma insulin-like growth factor-I level, and GH levels were suppressed to below 1.25 micrograms/L in 13 patients and to 1.3 micrograms/L in 1 subject during an oral glucose tolerance test. As we found a highly significant difference in GH secretion between male and female controls, the results obtained in patients were compared with those in their gender- and age-matched controls. Patients with active acromegaly displayed a significantly higher number of deconvolution-estimated secretory bursts (31/24 h in males and 27/24 h in female patients). The estimated secretion rate per 24 h was 25 times greater in female acromegalics and 100 times greater in male acromegalics than that in the controls. In patients with active acromegaly, about 50% of the GH was secreted in a nonpulsatile fashion. In contrast, normal subjects and patients shortly after pituitary surgery secreted GH predominantly (> 99%) in a pulsatile manner. By deconvolution analysis, the mean plasma half-life of GH was 19.7 min in treated male patients and 19.5 min in treated female patients (P = NS vs. controls) estimated mean total GH production/day, 188 micrograms in males and 240 micrograms in females (P = NS vs. controls); number of secretory bursts/24 h, 19.3 in males and 21.9 in females (P = NS vs. controls). In addition, we could not establish any difference in pulse characteristics with Cluster analysis between surgically treated patients and their control subjects. The present data suggest that the basic abnormality of acromegaly resides in the pituitary gland rather than in the hypothalamus.