DIAGNOSING GROWTH-HORMONE DEFICIENCY - THE VALUE OF SHORT-TERM HYPOCALORIC DIET

In the attempt to define possible causes of false positive GH deficien cy, the role of caloric intake on GH determination was explored. The s erum GH responses to insulin-induced hypoglycemia or arginine were ass essed before and after 3 days of a hypocaloric diet in 23 prepubertal children of normal weight, aged 6.7-11.9 yr. Seventeen had short statu re and a GH response to insulin and arginine below 10 mu g/L, and 6 co ntrols had normal stature and a GH peak above 10 mu g/L in response to arginine. After diet, the serum peak GH and the area under the curve increased in both the patients (P < 0.0005 and P < 0.0005) and the con trols (P < 0.005 and P < 0.025) with a GH peak greater than 10 mu g/L in 11 of 17 patients. The patients with a persistent GH response below 10 mu g/L also had lower mean 12-h overnight GH levels (P < 0.0005), whereas those with a normal GH response after diet had an overnight GH level greater than 3 mu g/L. In the patients, the mean nighttime GH c oncentrations correlated with the serum GH peak (r = 0.85; P < 0.005) and with the area under the curve after the diet (r = 0.65; P < 0.025) . The diet induced changes in plasma insulin-like growth factor-I, GH- releasing hormone levels, basal blood sugar and the nadir level obtain ed during insulin stimulation, total T-3, and rT(3). Height increased significantly during 1 and 2 yr (P < 0.005) of GH treatment only in pa tients with a GH response below 10 mu g/L after the diet. These data a re consistent with the hypothesis that the GH response to stimulation is strongly calorie dependent and that 3 days of a hypocaloric diet ca n increase the number and height of GH peaks and the total GH response s to insulin and arginine. The clear correlation of the GH response to stimulation after a hypocaloric diet with the mean nighttime GH and a lso with the growth response to GH treatment indicates that GH deficie ncy may be overdiagnosed in many children with short stature.