Changes in body composition, adipokines, ghrelin, and FGF23 in growth hormone-deficient children during rhGH therapy.

Introduction: Beyond growth acceleration, growth hormone (GH) therapy improves body composition of GH-deficient (GHD) children due to the interaction of GH with lipid and carbohydrate metabolism, possibly mediated by adipokines secreted by adipose tissue and ghrelin. To promote linear growth, it is essential to have normal phosphate homeostasis. Fibroblast growth factor 23 (FGF23) is a known regulator of serum phosphorus and may be responsible for the increased renal phosphorus reabsorption observed during GH therapy. This study aimed to assess the impact of one-year GH therapy on body composition, adipokines, acylated/unacylated ghrelin (AG/UAG), and FGF23 in GHD children.

Material and methods: A prospective observational study of 42 prepubertal, non-obese GHD children followed up in the first year of GH replacement therapy, investigating changes in adipokine profiles, AG/UAG, FGF23, and body composition. Data before therapy onset were compared with measurements obtained after 6 and 12 months of GH therapy.

Results: All children with a mean age of 9.2 ± 2.6 years grew at an accelerated pace. Total body fat decreased significantly, while the lipid profile improved, and total bone mineral density (BMD) significantly increased over the 12 months of treatment. Leptin and UAG levels decreased significantly, whereas adiponectin and AG values increased. A significant increase in plasma FGF23 and insulin growth factor 1 (IGF1) was accompanied by increased serum phosphate. Changes in FGF23 concentration did not have an impact on BMD. The strong association of FGF23 with IGF1 and height standard deviation (SD) could reveal a role of FGF23 in linear growth. In regression analysis models, GH therapy influences the changes of leptin and adiponectin, but not ghrelin, independently of body composition - lean or fat mass.

Conclusions: GH replacement therapy improves body composition and adipokine profile in GHD children and directly impacts leptin and adiponectin concentrations independently of body composition. Also, GHD children have increased serum phosphate, correlated with upregulation rather than with suppression of FGF23, an unexpected observation given the phosphaturic role of FGF23. Further research is needed to identify the molecular mechanisms by which the GH/IGF1 axis influences adipokines secretion and plasma changes of FGF23.