Association of serum creatinine-to-albumin ratio with hyperandrogenemia and low sex hormone-binding globulin in women of reproductive age: a cross-sectional analysis of NHANES 2013–2016

BACKGROUND: Hyperandrogenemia (HA) and low sex hormone-binding globulin (SHBG) are core features of polycystic ovary syndrome. The creatinine-to-albumin ratio (CAR), a simple renal-nutritional marker linked to female infertility, has not been studied in relation to HA or low SHBG. OBJECTIVE: To examine the association of CAR with low SHBG and HA, defined by the free androgen index (FAI), in U.S. women of reproductive age. METHODS: In this cross-sectional analysis of NHANES 2013-2016, we included 683 women aged 18-49 years. CAR (serum creatinine/albumin) was categorized into tertiles; low SHBG was defined as < 30 nmol/L and HA as FAI ≥ 75th percentile. Survey-weighted multivariable logistic regression was used, with multiple imputation (m = 5) as a sensitivity analysis. RESULTS: for trend = 0.044). In Model 2 (plus smoking, BMI, low HDL-C), associations attenuated (OR 1.95, 95% CI 1.05-3.64 for low SHBG; 1.24, 95% CI 0.65-2.34 for HA-FAI). HA defined by total testosterone was not associated with CAR. CONCLUSION: Higher CAR was associated with low SHBG and FAI-defined HA after demographic adjustment, with attenuation after metabolic adjustment, suggesting confounding by shared metabolic factors. As CAR derives from routine laboratory tests, it may be a practical marker of reproductive metabolic risk; the cross-sectional design precludes causal inference.