Fe is an essential element for erythropoiesis and Hb synthesis. High Hb levels affect the blood’s viscosity and are associated with cardiovascular dysfunction. The aim of the present study was to examine relationships of Hb and cardiometabolic abnormalities with the risk of alanine aminotransferase (ALT) elevation in adolescents.

A population-based, cross-sectional study.

National Nutrition and Health Survey in Taiwan (2010–2011, adolescents).

Healthy adolescents aged 13–18 years.

In total, 1941 adolescents (963 boys and 978 girls) were entered in the study. The mean age was 15·3 (sd 0·1) years (boys, 15·3 (sd 0·1) years; girls, 15·2 (sd 0·1) years). ALT tertile cut-off points for boys were 11 and 16 U/l, and for girls were 9 and 12 U/l. Girls without dyslipidaemia and presenting in the highest quartile (Q1) of Hb (>13·6 g/dl) were 1·89 and 3·76 times more likely to have raised serum ALT (9 and >12 U/l, respectively) than the reference (lowest quartile of Hb (Q1), <12·4 g/dl). Moreover, for those girls with dyslipidaemia, serum ALT seemed to increase with an increase in Hb levels. Specifically, girls with dyslipidaemia and Hb levels of 12·4, 13·1 and 13·6 g/dl were, respectively, 2·86, 3·53 and 5·64 times more likely to have elevated serum ALT levels (>12 U/l) than the reference (Q1 of Hb, <12·4 g/dl). The only effect found in boys was for those who had dyslipidaemia and presenting in Q4 of Hb (>15·4 g/dl), who were 7·40 times more likely to have elevated serum ALT of >16 U/l than the reference (Q1 of Hb, <14·1 g/dl).

Our findings suggest that an increased Hb level is a predictor of elevated serum ALT in adolescent girls with dyslipidaemia. Our study also highlights the importance of further research to establish cut-off points for Hb and its utility in diagnosing and preventing the onset of dyslipidaemia in adolescents.