79 Growth hormone (GH) response to growth hormone releasing factor (GRF) in Turner Syndrome

Abstract

Growth hormone deficiency has been described in association with Turner Syndrome, but its mechanisms are unknown.

Seventeen prepubertal girls with Turner Syndrome (age 6 5/12 to 15 8/12 years; height - 5,4 to-1,8 SD; weight 93% to 169% of ideal body weight - IBW -) underwent a stimulation test with GRF (0,5 mcg/kg). Plasma GH was measured by radioimmunoassay from - 30 to + 120 minutes. These responses were compared to those we previously reported in children with constitutional short stature - controls - (Hormone Res. 22 : 32, 1985).

Peak Plasma GH after GRF was 17,0 ± 3,6 ng/ml (mean ± SEM), significantly lower (p < 0,001) than in control children (39,2 ± 5,1 ng/ml). In Turner patients, peak GH value was negatively correlated with the % of IBW (r=-0,58, p < 0,02), the % of body fat (r=-0,59, p < 0,02) and the body mass index (r=-0,54, p < 0,05). Baseline plasma insulin-like growth factor (IGF-I) was within the normal range for prepubertal children, with a mean ± SEM of 0,77 ± 0,09 U/ml.

In conclusion, prepubertal girls with Turner Syndrome have a blunted GH response to GRF; in contrast to children with hypothalamo-pituitary insufficiency, they have normal plasma IGF-I. Our data suggest that the decreased GH response to GRF of Turner Syndrome patients may result from excess body fat.

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