Divergence between growth hormone and insulin-like growth factor-I concentrations in the follow-up of acromegaly

Context: Divergence between GH and IGF-I values is regularly observed in treated acromegalic patients, and its significance is unclear. Objectives: The objective of the study was to explore the frequency and identify potential determinants of discordant serum GH and IGF-I concentrations in noncured acromegalic patients. Patients: Two hundred twenty-nine noncured acromegalic patients of the Belgian acromegaly registry (AcroBel) were grouped according to their mean GH level (<= or > 2 mu g/liter) and IGF-I z-score (<= 2 or > 2). Clinical and metabolic parameters were compared between groups with active disease (high GH and IGF-I; n = 81), high GH (with normal IGF-I; n = 25), high IGF-I (with normal GH; n = 55), and controlled disease (GH and IGF-I normal; n = 68). Results: Compared with the high IGF-I group, the high GH group was characterized by younger age (52 vs. 58 yr, P < 0.05), female predominance (72 vs. 36%, P < 0.01), and lower body mass index (25 vs. 31 kg/m(2); P < 0.001), fasting glucose (91 vs. 99 mg/dl; P < 0.05), and glycated hemoglobin levels (5.7 vs. 6.1%; P < 0.01). There was no difference among the groups regarding baseline characteristics of pituitary adenoma, current medical treatment, or symptom score. Conclusions: Thirty-five percent of noncured acromegalic patients exhibit a discordant GH and IGF-I pattern. The high GH phenotype was found predominantly in younger estrogen-sufficient females, implying a possible role for age, gender, and estrogens in this biochemical divergence. The high IGF-I phenotype was associated with a worse metabolic profile, suggesting that high IGF-I, rather than high GH, is indicative of persistently active disease.