Association of Serum 25-hydroxyvitamin D Levels and Liver Enzymes in a Nationally Representative Sample of Iranian Adolescents: The Childhood and Adolescence Surveillance and Prevention of Adult Noncommunicable Disease Study.

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

Methods: This population-based cross-sectional survey was conducted among a nationally representative multistage sample of 1095 adolescents (52% boys), aged 10-18 years, living in different provinces of Iran. Serum 25(OH)D concentration <30 ng/mL was considered as hypovitaminosis D, and liver enzymes (alanine aminotransaminase [ALT] and aspartate aminotransaminase [AST]) of >40 U/L was considered 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 ratios (95% confidence interval) of serum 25(OH)D and elevated liver enzymes were assessed by logistic regression analysis.

Results: 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.

Conclusions: 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.