Association of serum 25-hydroxy vitamin D levels and liver enzymes in a nationally representative sample of Iranian adolescents: the CASPIAN III Study

Headnote

Keywords: Vitamin D, liver function tests, adolescents

Background: Hypovitaminosis D is highly prevalent, and has several adverse health effects. This study aimed to assess the relationship of serum concentrations of 25- hydroxy vitamin D [25(OH)D] and liver enzymes in adolescents.

Methods: This population-based cross-sectional survey was conducted among a nationally representative multi- stage sample of 1095 adolescents (52% boys), aged 10-18 years, living in different provinces of Iran. Serum 25(OH)D concentration<30ng/mL was considered as hypovitaminosis D, and liver enzymes (alanine aminotransaminase, ALT and aspartate aminotransaminase, AST) of > 40 U/L as high level. To determine the association between serum 25(OH)D categories and elevated levels of liver enzymes, multiple regression models and linear regression analysis were applied, after adjustment for potential confounders. Odds ratio (OR) 95% confidence interval (CI) of serum 25(OH)D and elevated liver enzymes were assessed by logistic regression analysis.

Findings: Higher rates of vitamin D deficiency were documented among individuals with increased levels of liver enzymes. Compared to boys, median of 25(OH)D was lower in girls with elevated levels of liver function tests (12.75 vs. 25.60 ng/mL for ALT, and 13 vs.14.10 ng/mL for AST), with marginally significant gender differences regarding AST.

Conclusion: We found a relatively high frequency of hypovitaminosis D among adolescents with abnormal liver function. Further prospective studies are needed to examine these associations from early life.