The relationship between serum GH and serum IGF-I in acromegaly is gender-specific

In patients with acromegaly, there is a linear association between log(10) serum GH and IGF-I. Healthy females secrete three times more GH than males but have broadly similar serum IGF-I levels, and in adult GH deficiency, th e dose of exogenous GH required to achieve a given serum IGF-I is significa ntly greater in females than males. We report the influence of gender on th e relationship between serum GH and IGF-I in subjects with active acromegal y. A single, fasted, serum sample was obtained from 153 subjects with activ e disease (87 males; median age, 47.8 yr; range, 20-82 yr) in whom serum IG F-I was at least 30% above the upper limit of an age-related reference rang e after washout from medical therapy. A linear correlation between serum IG F-I and log(10) serum GH was observed (r = 0.53; P < 0.0001), but this rela tionship was significantly influenced by gender. For a given serum GH value , females were estimated to have serum IGF-I values 82 ng/ml less than male s [P < 0.02; 95% confidence interval (CI), 15.2-149]. In females receiving oral E, mean serum IGF-I for a given GH value was 130 ng/ml lower than in m ales (P = 0.01; 95% CI, 29.8-230.2) but only 60 ng/ml less than the remaini ng 45 females (NS; P = 0.2). This study demonstrates a gender difference in the relationship between serum GH and IGF-I in patients with active acrome galy consistent with relative GH resistance observed in normal and GHD fema les, which may, in part, be mediated by E. This observation has important i mplications for the use of IGF-I as a measure of disease activity.