ALTERATIONS IN GROWTH-HORMONE SECRETION AND CLEARANCE IN ADOLESCENT BOYS WITH INSULIN-DEPENDENT DIABETES-MELLITUS

At puberty, elevated circulating GH concentrations are found, with a p arallel increase in the levels of insulin-like growth factor-I (IGF-I) . However, these hormonal changes are less well understood in children with insulin-dependent diabetes mellitus (IDDM) during the peripubert al years. Since the metabolic derangement is often associated with ele vated circulating GH and diminished serum IGF-I levels, we sought to d etermine whether similar alterations occur in boys with IDDM. A multip le parameter deconvolution analysis was applied to serum GH concentrat ions measured at 20-min intervals for 24 h in 25 boys with IDDM. Subje cts were divided into 3 pubertal groups, pre (n = 9), early (n = 8), a nd late (n = 11), according to Tanner stage. Glycosylated hemoglobin a nd body mass indeX-SD scores were indistinguishable among groups. Fort y nondiabetic peripubertal boys served as controls. Similar to those i n the normal boys, circulating GH concentrations and serum IGF-I level s increased during puberty in the boys with IDDM. The augmented circul ating GH concentrations occur due to an increase in GH secretion, as d etermined by calculated daily GH production rates (760 +/- 119 vs. 102 5 +/- 121 vs. 1821 +/- 266 mug/day, respectively for the 3 groups). IG F-I levels were decreased in prepuberty in the boys with IDDM and were overcome with increasing pubertal development (0.68 +/- 0.13 vs. 0.78 +/- 0.11 vs. 1.53 +/- 0.20 U/mL; P < 0.05). There was an increase in the maximal rate of GH secretion per burst (amplitude) during prepuber ty (0.54 +/- 0.05 vs. 0.88 +/- 0.17 mug/L.min, control vs. IDDM; P = 0 .03) and early puberty (0.64 +/- 0.10 vs. 0.88 +/- 0.10 mug/L . min; P = 0.04). The differences in amplitude between the controls and the bo ys with IDDM were absent once puberty was well established (1.00 +/- 0 .10 vs. 1.02 +/- 0.14 mug/L . min; P > 0.05). The metabolic clearance of GH was increased in the late pubertal boys with IDDM compared to th at in their controls (GH half-life, 24.0 +/- 1.0 in control vs. 19.8 /- 0.5 min in diabetics; P = 0.006). We conclude that comparable incre ments in GH secretion and serum IGF-I levels in boys with IDDM in mode rate glycemic control and controls are presumably related to increased levels of testosterone in both groups. However, differences exist wit h respect to GH secretory burst amplitude (augmented) and serum IGF-I concentrations (decreased) before puberty is reached. These alteration s disappear with the establishment of puberty.