Self-reported female hormone therapy history and thyroid disorder burden among postmenopausal Korean women: a cross-sectional KNHANES IV study

Menopausal hormone therapy (MHT) and thyroid disorders commonly intersect in postmenopausal care, but East Asian population evidence on thyroid disorder burden among women with a self-reported history of female hormone therapy is limited. We conducted a cross-sectional analysis of postmenopausal women in KNHANES IV (2007–2009). Exposure was questionnaire-recorded history of female hormone medication use, which did not identify current use or treatment details. Outcomes were doctor-diagnosed (primary), current, lifetime, and treated thyroid disorder. Survey-weighted logistic regression adjusted for demographic, socioeconomic, metabolic, reproductive, and survey-year factors. Benjamini-Hochberg-adjusted q values controlled false discovery across the four outcomes. Sensitivity analyses addressed covariates, menopause timing, healthcare contact, age restrictions, survey cycle, missingness, and gravidity; duration was exploratory. The analysis included 3,974 women; 582 reported a female hormone therapy history. Weighted prevalence was higher with versus without a history for doctor-diagnosed (10.87% vs. 6.87%), current (6.79% vs. 3.79%), lifetime (10.95% vs. 6.96%), and treated thyroid disorder (4.88% vs. 2.95%). Female hormone therapy history was associated with doctor-diagnosed (adjusted odds ratio [OR] 1.52, 95% confidence interval [CI] 1.06–2.16; q = 0.031), current (OR 1.75, 95% CI 1.09–2.83; q = 0.031), and lifetime thyroid disorder (OR 1.50, 95% CI 1.06–2.14; q = 0.031); the thyroid-treatment estimate was less precise (OR 1.60, 95% CI 0.96–2.68; q = 0.071). The primary estimate attenuated after expanded adjustment (OR 1.38, 95% CI 0.96-2.00) and remained positive after healthcare-contact adjustment (OR 1.46, 95% CI 1.01–2.10), while age-restricted estimates crossed the null. Gravidity adjustment gave a similar estimate (OR 1.52, 95% CI 1.05–2.20); duration results were heterogeneous. Women reporting a female hormone therapy history had a higher concurrent burden of questionnaire-defined thyroid disorder. This cross-sectional association may reflect clinical history, ascertainment, or residual confounding and does not establish temporality or causality. It does not support universal thyroid screening or MHT changes solely on the basis of female hormone therapy history.