International Journal of Environmental Research and Public Health · Jul 21, 2026

Age-Metabolic Profile of Lower Serum Estradiol Among Women in Kazakhstan: A Large National Survey-Based Analytical Study

By Sadykov B, Ibrayeva A, Ismoldayev Y et al.

Serum estradiol is a central biomarker of female reproductive biology and is also linked to bone, metabolic, and cardiovascular health. Population-level data on estradiol distribution among women in Kazakhstan remain limited, and it is unclear whether lower estradiol categories in national survey data reflect geographic clustering or individual age-metabolic composition. We performed a secondary analysis of a large national survey-based analytical sample from Kazakhstan using the WHO STEPS framework. The analytical sample included 3498 women aged 18-69 years with available serum estradiol measurements and core covariate data. The primary binary outcome was a lower-tail estradiol category defined as E2 < 200 pmol/L, corresponding approximately to the empirical lower quartile of the analytical female subsample. Descriptive statistics, age-specific quartile summaries, multivariable logistic regression, continuous-outcome regression for ln(E2), nonlinearity diagnostics, and regional heterogeneity analyses were used. Median serum estradiol was 313.00 pmol/L (interquartile range 207.25-457.00). In unweighted and unadjusted analytical-sample comparisons, there was little evidence of regional heterogeneity in estradiol distribution (ANOVA p = 0.583; Kruskal-Wallis p = 0.287; eta-squared = 0.0049; ICC for ln[E2] = 0.000861). In the multivariable model, compared with women aged 18-29 years, the odds of belonging to the lower-tail estradiol category increased from the 40-49-year group (aOR 1.82, 95% CI 1.31-2.53) to the 50-59-year group (aOR 3.72, 95% CI 2.60-5.33) and were highest in the 60-69-year group (aOR 7.48, 95% CI 5.23-10.70). Overweight and obesity were associated with higher odds of lower-tail estradiol, and low HDL cholesterol showed a modest independent association (aOR 1.26, 95% CI 1.04-1.53). In this large national survey-based analytical sample of women, lower-tail estradiol was more closely characterized by age, adiposity, and HDL cholesterol than by regional clustering. The lower estradiol category used in this study should not be interpreted as a clinical diagnosis of hypoestrogenism, particularly because reproductive-stage information was unavailable.

doi.org/10.3390/ijerph23070934Open accessPubMed 42512238Populations