ABNORMAL PULSATILE SECRETION OF GROWTH-HORMONE IN NON-INSULIN-DEPENDENT DIABETES-MELLITUS

OBJECTIVE Studies of GH secretion in patients with non-insulin depende nt diabetes mellitus (NIDDM) have produced conflicting results. We aim ed to differentiate the effects of obesity and metabolic control on pu lsatile GH secretion in patients with NIDDM. DESIGN Blood sampling eve ry 15 min from 22.00 hours to 08.00 hours after a fasting period of at least 3 h. Patients: 13 male NIDDM patients, 9 healthy control subjec ts matched for age and BMI, and 6 lean subjects matched for age. MEASU REMENTS Measurement of GH by a novel ultrasensitive chemiluminescence assay. Analysis of concentration vs time profiles by a multiparameter deconvolution technique. RESULTS GH burst frequency was increased in t he NIDDM (0.82 +/- 0.28 h(-1)) compared with both control groups (lean : 0.6 +/- 0.11; obese: 0.56 +/- 0.19). GH burst mass was decreased in patients (1.57 +/- 0.98 mu g/l.min) and in obese controls (1.46 +/- 1. 44) compared to lean controls (3.71 +/- 3.88). These differences resul ted in a significantly higher nocturnal pulsatile GH secretion rate in the lean compared to the obese controls, whereas in the patient group enhanced GH burst frequency compensated for reduced burst mass. The c haracteristics of GH secretion were not related to nocturnal or early morning blood glucose concentrations. However, GH secretion rate was c orrelated positively with HbA(1c) (r = 0.57; P=0.04), and negatively w ith plasma C peptide concentrations. CONCLUSIONS The specific increase in GH burst frequency previously described in insulin-dependent diabe tes mellitus is also present in NIDDM. However, GH hypersecretion does not occur because GH burst mass is reduced in proportion to the degre e of obesity. The effect of diabetes on the hypothalamic control of GH release appears to be determined by the quality of long-term glycaemi c control.