Irisin levels in children with growth hormone (GH) deficiency are lower compared with those of the general population, but treatment with GH replacement can raise irisin levels, according to results from a study published in the Journal of Clinical Endocrinology & Metabolism.
Irisin is a newly identified myokine and data suggest that it may play an essential role in regulating adipose tissue metabolism by converting white to brown adipose tissue. As irisin levels affect both adipose tissue and glucose metabolism, changes in irisin could mediate the effects of GH deficiency and GH replacement on these end points. The current study evaluated associations between circulating irisin levels and any body composition and metabolic parameters in 54 prepubertal children (mean age, 7.4 ± 0.8 years) with idiopathic GH deficiency who were treated with growth hormone for ≥12 months. A group of 31 healthy short children comprised the control group.
At baseline, children with GH deficiency had lower growth velocity (P <.001), GH peak after stimulation tests (both P <.001), and insulin-like growth factor 1 (P <.001) compared with controls, along with significantly lower irisin (P <.001) and higher body mass index (P <.001) and waist circumference (P =.001). There was no significant difference between groups in other metabolic parameters.
After 12 months of treatment with GH replacement, there was a significant increase in height (P <.001), growth velocity (P <.001), and insulin-like growth factor 1 (P <.001), fasting glucose (P =.002), fasting insulin (P <.001), and irisin (P =.005) levels. This was accompanied by a decline in body mass index (P =.001) and waist circumference (P =.003).
Overall, whereas IGF-1 is considered the main biochemical marker for GH replacement, irisin levels may be a metabolic marker for treatment. The researchers noted that because there are no similar studies on irisin in this population, “these data should be considered as preliminary and whether the association between GH and irisin is casual or not remains to be demonstrated by future studies with larger populations.”
Ciresi A, Pizzolanti G, Guarnotta V, Giordano C. Circulating irisin levels in children with growth hormone (GH) deficiency before and after 1 year of GH treatment [published online November 9, 2018]. J Clin Endocrinol Metab. doi:10.1210/jc.2018-01440