Factors Attenuating Growth Promoting Effect of Growth Hormone Therapy for Turner's Syndrome.

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Abstract
Nine patients with Turner''s syndrome aged 7 to 13 years were treated with recombinant human growth hormone (hGH) at a dose of 0.5 or 1.0 U/kg/w for 1 year. In five of them the growth rate was accelerated from 3.3 .+-. 0.6 (SD) to 6.5 .+-. 0.5 cm/y (group A), whereas 4 had a reduced rate of growth promotion (3.4 .+-. 0.3 to 4.6 .+-. 0.4 cm/y) (group B). Analysis of factors affecting growth response to hGH revealed 3 major parameters: (1) age of initiating hGH therapy (A, 9.5 .+-. 2.1 vs B, 13.3 .+-. 0.4 yrs, P < 0.01), (2) basal LH (A, 3.2 .+-. 2.4 vs. B, 44.9 .+-. 17.8 mIU/ml, P < 0.001) and FSH levels (A, 17.7 .+-. 15.4 vs B, 131 .+-. 49 mIU ml, P < 0.01) and (3) somatomedin-C (SM-C) producing capacity: coefficient of correlation to growth rate, r = 0.80, P < 0.01). No remarkable changes were observed in the results of glucose tolerance, thyroid state, calcium metabolism and liver function tests. These results indicate that patient''s age is the most crucial factor in effective treatment with hGH, and in adolescent girls, gonadal failure with a limited increase in SM-C production attenuates the growth promoting potency of hGH.