The recently discovered myokine irisin has been implicated in several observational studies as a potential therapeutic target for obesity-related diseases. However, no information is available as to the heritability of this hormone. The present study aims to fill this gap. A total of 120 families (n=254; 121 adults and 133 children) were included in the study taken from the Riyadh Biomarkers Research Program cohort. Information gathered include anthropometrics, and glycaemic, lipid and adipocytokine profiles. Irisin was measured using ELISA. Examining heritability between mother and offspring, the most significant heritable traits in sons included irisin (P=1.6×10(-5)), systolic blood pressure (P=3.6×10(-4)), total cholesterol (P=3.5×10(-7)) and LDL (low-density lipoprotein)-cholesterol (P=1.2×10(-6)). Heritable traits between mother and daughter again included irisin (P<0.002), as well as anthropometric associations such as waist (P<0.01) and hip (P<0.005) circumference and blood pressure (P<0.002); biochemically, principal associations were observed with HDL (high-density lipoprotein)-cholesterol (P<0.04) and TNF-α (tumour necrosis factor-α) (P<0.002). HDL-cholesterol was the single most significant predictor for irisin levels in adults, explaining 17% of the variance, whereas in children AngII (angiotensin II) was the most significant predictor of irisin levels, explaining 19% of the variance (P=0.003). Circulating irisin appears to be maternally inherited and is predicted by HDL-cholesterol in adults and AngII in children, both factors influenced by energy expenditure and regulation. Taken together, these findings suggest a significant role of irisin in energy-generating processes.