Diagnostic limitations of spontaneous growth hormone measurements in normally growing prepubertal children
R. Lanes
Department of Endocrinology, Hospital Central Dr Carlos Arvelo, Venezuela.
To evaluate whether the measurement of the spontaneous overnight growth
hormone secretion in prepubertal children clearly separated normal children
from subjects with growth hormone deficiency, we studied 45 prepubertal
normally growing children (10 with normal height and 35 with constitutional
growth delay) and compared their overnight growth hormone secretion with
that of a group of subjects with either isolated growth hormone deficiency
or neurosecretory dysfunction. Peak growth hormone levels (greater than or
equal to 10 ng/mL) following oral clonidine administration were normal in
individuals with normal height, constitutional growth delay, and
neurosecretory dysfunction, as was the basal somatomedin C concentration;
subjects with growth hormone deficiency had low peak growth hormone levels
(less than 10 ng/mL) following oral clonidine administration as well as low
basal somatomedin C values. The mean 9-hour overnight growth hormone
concentration, total growth hormone output, total number of nocturnal
pulses, and the mean peak growth hormone response during nocturnal sampling
were similar in the normal height and constitutional growth delay groups
and significantly greater than those seen in subjects with either growth
hormone deficiency or neurosecretory dysfunction. Twelve (26.6%) of 45
normally growing children (4 to 10 normal height and 8 of 35 constitutional
growth delay), however, had low overnight growth hormone levels (less than
3 ng/mL), which overlapped results obtained in the growth hormone-deficient
or neurosecretory dysfunction groups. Frequent overnight growth hormone
(GH) sampling does not always separate normal-growing children from those
with partial or complete GH deficiency. In our this study over one quarter
of the normally growing children had overnight GH levels in the range of
children with either GH deficiency or neurosecretory dysfunction. These
findings, in addition to the cost and difficulty in performing this test,
do not support the measurement of spontaneous GH as a routine test in short
but normally growing prepubertal children.
