The GH-releasing hormone (GHRH) test in acromegaly before and after adenomectomy

The GHRH test may represent a new tool in the study of GH dynamics in acromegaly. GH responsiveness to GHRH 1–40 (50 µg iv) has been studied in 21 acromegalic patients. Nineteen out of 21 had active disease. Five patients were also studied 1–12 months after neurosurgery. Two apparently cured acromegalics were studied 1–2 yr after surgery. GH secretion has been evaluated in all patients by means of TRH, bromocriptine and insulin hypoglycemia tests, too. GH response to GHRH has also been performed in 14 normal subjects. In acromegaly, GH responses after GHRH (p < 0.01 vs placebo) were variable. The GH peak ranged from 8 to 445 ng/ml in patients with active disease. Maximum GH increase after GHRH (calculated as peak/basal value ratio) was significantly reduced in acromegaly (2.9 ± 0.5 ng/ml; mean ± SE) in comparison to controls (34.1 ± 10.9 ng/ml; p < 0.01). No significant differences in GH pattern after GHRH were found between untreated and previously treated patients with active disease. A significant correlation was found between GH basal levels and GH incremental area (p < 0.05) and between GH basal and peak levels (p < 0.01) after GHRH. A signifcant increase in PRL secretion was observed in acromegalic patients after GHRH (p < 0.01 vs placebo). No discernable variation was found in the other pituitary hormones pattern after the peptide administration. A positive correlation was observed between GH increase after GHRH and insulin hypoglycemia (p < 0.01). After surgery, GH increase after GHRH got up to the normal range only in cured patients. GH increase in these patients was significantly inversely correlated with Sm-C levels (p < 0.01). The phenomenon of a normal GH responsiveness to GHRH could be regarded as additional evidence of successful surgical therapy in acromegaly.