EFFECT OF HYPERSOMATOSTATINEMIA ON GROWTH-HORMONE SECRETION IN CYSTIC-FIBROSIS PATIENTS WITH DIABETES

We have recently shown that hypersomatostatinemia is a feature of cyst ic fibrosis (CF) when these patients have CF-associated pancreatogenic diabetes mellitus (CFDM). To address the possibility that patients wi th CFDM might have suppressed pituitary growth hormone (GH) release as a result of increased plasma somatostatin, GH secretion in 8 CFDM pat ients and 8 normal male controls was studied using a standard arginine infusion stimulus. Concentrations of the GH-dependent peptides, insul in-like growth factor I (IGF-I) and insulin-like growth factor binding protein 3 (IGFBP-3) were also measured. We found that mean GH concent rations in the CFDM group were significantly increased P<0.05) rather than decreased at the 30-min (12.3 +/- 3.6 vs. 3.8 +/- 1.9 ng/ml), 45- min (15.4 +/- 2.9 vs. 6.1 +/- 2.3 ng/ml) and 60-min (13.2 +/- 2.3 vs. 6.2 +/- 2.2 ng/ml) time points of study. Mean GH area under the curve (633 +/- 128 vs. 249 +/- 107 ng/ml) was also significantly greater (p< 0.05) in the CFDM group. Despite higher GH levels in the CFDM patients , their IGF-I and IGFBP-3 concentrations were low. We conclude that pl asma somatostatin elevations in the CFDM group are not of sufficient m agnitude to suppress pituitary GH release. Decreased levels of growth mediating peptides ill the relatively malnourished CF subjects suggest a pattern of malnutrition-induced GH resistance which may contribute to poor weight and height gain.