Endocrine Abstracts

Background: Assessment of nocturnal GH secretion is useful tool in diagnosing GH deficiency (GHD) in children. The time period of the evaluation, the number of blood samples, as well as the choice of cut-off value for this examination – are still the matter for discussion.

Aim: The aim of the study was to compare the results of 2-h and 6-h assessment of nocturnal GH secretion in children with suspected neurosecretory dysfunction of GH secretion (NSD).

Material and methods: The analysis comprised the results of 2-h and 6-h assessment of nocturnal GH secretion in 33 short children with GH peak normal in stimulating tests (>10 ml) but decreased in 2-h nocturnal assessment (<16 ng/ml – i.e. the cut-off value with most accuracy in diagnosing GHD, according to ROC analysis) and decreased IGF-I secretion. The 6-h nocturnal profile was performed after approximately 6 months from the first evaluation. The blood samples for GH measurement were obtained in both tests every 30 min.

Results: GH peak in the first 2-h test was 8.5±4.5 ng/ml, being significantly (P<0.05) higher in the second test: 12.3±6.5 ng/ml during 2 h and 13.5±6.9 ng/ml during 6 h of profile. The results of the second evaluation were consistent with those of the first test in 24 children, while in the remaining 9 cases nocturnal GH secretion in repeated assessment presented over the cut-off level. In the 6-h profile, the highest GH peak was observed during first 2 h in 26 patients, while later – only in 7 children. However, in just 1 case only, the earliest value that exceeded the cut-off level was obtained later than during first 2 h of the test.

Conclusions: Repeated assessment of nocturnal GH secretion may prevent overdiagnosing NSD in children. It seems no necessary to assess 6-h nocturnal GH profile in such cases.