Abstract
An increased spontaneous and stimulated growth hormone (GH) secretion is well documented
in insulin-dependent diabetes mellitus. On the contrary, in non-insulin-dependent
diabetes mellitus (NIDDM) conflicting results arise from literature. In 14 patients
with NIDDM, 7 normal weight (NWD) and 7 obese (OD), we investigated the somatotrope
responsiveness to GHRH (1 µg/kg) alone or combined with arginine (ARG, 0.5 g/kg),
which is able to enhance the GH response to GHRH, probably by inhibiting somatostatin
release from hypothalamus. Baseline IGF-I, IRI, FFA and glucose levels were also determined.
Twelve healthy normal subjects (NS) and 12 obese patients (OP) were evaluated as control
groups. GH but not IGF-I levels were higher (p < 0.05) in NS than in OP (1.5 ± 0.5
vs 0.5 ± 0.2 µg/l). Insulin levels were higher (p < 0.05) in OP than in NS, NWD and
OD (18.7 ± 1.8 vs 8.7 ± 0.5, 6.4 ± 1.9 and 11.8 ± 1.2 µU/l). FFA were higher (p <
0.05) in NWD, OD and OP than in NS (0.69 ± 0.04, 0.70 ± 0.04 and 0.65 ± 0.06 vs 0.39
± 0.03 mmol/l). Plasma glucose was higher (p < 0.05) in diabetic patients than in
normal and obese subjects. GH responses to GHRH in NWD, OD and OP were similar (AUC:
221.6 ± 33.3, 206.0 ± 35.9 and 177.2 ± 57.3 µg/l/min, respectively) and all lower
(p < 0.05) than that in NS (776.7 ± 206.5 µg/l/min). ARG determined a significant
increase of GHRH-induced GH release in all groups (p < 0.01). Again the GH responses
to ARG + GHRH in NWD, OD and OP were lower (p < 0.05) than that observed in NS. In
conclusion, our results demonstrate that, irrespective of body weight, patients with
non-insulin-dependent diabetes mellitus had an impairment of GH responses to GHRH
alone or combined with arginine. This finding may be explained by the presence of
high FFA levels which are known to inhibit GH secretion.
Key words
GH - FFA - NIDDM - Obesity
