Irisin Concentrations in Children and Adolescent Cancer Survivors and Their Relation to Metabolic, Bone, and Reproductive Profile: A Pilot Case–Control Study

<b>Background/Objectives</b>: Childhood cancer survivors (CCS) experience chronic health problems and significant metabolic burden. Timely identification of CCS at higher metabolic risk requires novel biomarkers. Irisin, a novel myokine/adipokine has been associated with metabolic, bone and reproductive diseases, but its role in the health of CCS is unknown. The aim of this study was to examine irisin concentrations in children and adolescent CCS (vs. controls) and their association with metabolic, bone and hormonal parameters. <b>Methods</b>: Children and adolescent CCS, aged 8-18 years, as well as healthy controls, underwent a detailed physical, body composition, biochemical, hormonal and serum irisin assessment at least 6 months post-treatment. <b>Results</b>: A total of 59 children and adolescents (36 CCS, 23 controls; mean age ± SD 12.8 ± 2.9 years; 10 prepubertal, 49 pubertal) participated in the study. Serum irisin concentrations (ng/mL) were significantly lower in CCS than controls [median (IQR) 6.54 (4.12) vs. 11.70 (8.75) ng/mL, respectively, <i>p</i> < 0.001]. In the total study sample, serum irisin was correlated negatively with LH (r_s = -0.314, <i>p</i> < 0.05), CRP (r_s = -0.366, <i>p</i> < 0.005), age (r_s = -0.323, <i>p</i> < 0.05) and positively with ALP (r_s = 0.328, <i>p</i> < 0.05). Serum irisin was also positively correlated with ApoB and Lpa (r_s = 0.410 and 0.421, respectively, <i>p</i> < 0.05) in CCS, and with PTH (r = 0.542, <i>p</i> < 0.005) in controls. Multivariate linear regression analysis indicated parathyroid hormone (PTH) as the only independent variable affecting irisin concentrations. <b>Conclusions</b>: Study results reinforce the irisin-PTH interplay hypothesis. Future studies are needed to clarify the potential role of irisin as a bone biomarker of CCS in childhood and adolescence.