Summary
Serum somatomedin-C (SM-C) and somatomedin (SM) concentrations were measured by, respectively,
radioimmuno (SM-C RIA) and radioreceptor assays (SM RRA) in 3 groups of children with
short stature. The patient population was different from previously reported series
in that it was urban Brazilian, low income, and significantly older. Group A consisted
of 6 male and 3 female children, aged 7.7-16.0 years, whose average peak plasma immunoreactive
growth hormone (GH) was above 10 ng/ml. Group B contained 8 male and 5 female untreated
GH-deficient patients, ranging in age from 9.5 to 21.0 years. In Group C there were
4 male and 1 female GH-deficient subjects treated with I.M. injections of GH (0.1
U/kg) from 1 month to 7 years.
The mean±SE basal RIA SM-C (ng/ml) concentrations were significantly lower in groups
B (34.2±8.8) and C (43.8±13.7) than A (214.3±42.7): A × B, P < 0.001 and A × C, P
< 0.02. Likewise the mean±SE basal RRA SM (ng/ml) concentrations were significantly
lower in groups B (78.9±17.6) and C (90.8±19.3) than group A (316.3±43.0): A × B,
P < 0.001 and A × C, P < 0.002. A significant linear correlation was observed between
RIA and RRA in group B (r=0.84; P < 0.001) and C (r=0.96; P < 0.01), but not for A
(r=0.61; P > 0.05).
Both the serum SM-C RIA and SM RRA were equally useful in differentiating children
with short stature and normal GH dynamics from untreated and treated GH-deficient
children. Part of the reason for this finding could be the significantly older age
of our children than previously reported. After GH treatment of GH-deficient children.
SM-C and SM values failed to return to normal and did not correlate with the increase
in height velocity. This is consistent with GH-induced stimulation of local SM production
being the important parameter as opposed to the serum SM-C level.
Key-Words
Somatomedin
-
Growth Deficiency
-
hGH Treatment
