April - June 2007, Volume 3, Issue 2

Popa M, Stefanescu AM, Procopiuc C, Dumitrescu C

Serum leptin and leptin binding activity after ten days administration of rHGH (as IGF-1 generation test) in short children

Acta Endo (Buc) 2007, 3 (2): 161-168
doi: 10.4183/aeb.2007.161

Leptin seems to play a significant role in the regulation of pituitary GH secretion. In GH deficient children serum leptin level is higher than in GH sufficient ones. Administration of rhGH resulted in a significant decrease in serum leptin in GH deficient but also in children displaying idiopathic growth delay, small for gestational age at birth, Prader-Willi syndrome and other obese. LBA is in fact the soluble form of leptin receptor. It was previously shown that GH deficient children are mostly hyperleptinemic and that GH induces a reduction in leptin level within 3 weeks of therapy. Such a reduction could serve as a valuable marker of the long term growth response. Twenty short children whose GH status was previously assessed through GH provocative tests and auxological evaluation were explored as concerns IGF I, leptin and LBA. According to these criteria they were classified as GH-deficient and GH-sufficient. Blood samples for the assay of serum leptin and LBA and IGF I were drawn at 8 a.m. A daily dose of 0.35 mg of rhGH was given subcutaneously at 8 pm in 12 of them and the same sampling was done 12 hours after the last injection. A therapy with GH with the same preparation and in comparable weekly dosage was started in all children and the height gain was evaluated after six months. Total serum leptin was assayed by a commercially available sandwich ELISA kit. LBA was assayed by a sandwich ELISA kit using a human IgG-Fc fragment of leptin receptor. IGF I determination was performed by the OCTEIA kit in a two-site immunoenzymometric assay (IEMA). The means and SEM before and after 10 days of GH administration in the whole group were of 3.4 ? 0.71 ng/ml and 1.7 ? 0.16 (p< 0.02) for leptin 0.27.1 ? 0.92 U/ml and 23.6 ?1.66 (ns) for LBA, 48.9 ? 10.65 ng/ml and 84.3 ? 17.61 for IGF I (p> 0.05, ns). Comparison between GH deficient (def) and GH sufficient (suf) subgroups resulted in significant differences as regards initial values for IGF I (20.2 ? 4.21 in def vs 77.6 ? 16.7 in suf, p< 0.02) but not in leptin, LBA, height and weight z scores. After ten days of therapy no significant differences were noted in subgroups for leptin, LBA and IGF I (absolute values), but a striking difference was noted in percentual rise of IGF I in def children. There was a significant positive correlation between leptin basal level and the growth rate in the subsequent 6 months of GH therapy. No similar correlation was noted for IGF I and LBA. It was concluded that hyperleptinemic GH deficient children seem to be particularly sensitive to the growth promoting effect of rhGH at least in the first six months of therapy.

Keywords: leptin, leptin binding activity, IGF I, GH deficiency, GH therapy, child

Correspondence: M. Popa, Dept. of Pediatric Endocrinology, Institute of Endocrinology, 34 Bd. Aviatorilor, 011863, Bucharest, Romania