Women's Thyroid Cancer Risk May Be Linked to Reproductive Lifespan and Hormone Therapy
核心洞察
A nationwide Korean study of 5.7 million women found that longer reproductive lifespan is associated with progressively increased thyroid cancer (搜索) risk.
Hormone replacement therapy (搜索) use was linked to elevated thyroid cancer (搜索) risk, with a stronger association observed among women receiving HRT for five years or more.
The study reported an incidence rate of approximately 2.4 per 1,000 people per year for thyroid cancer (搜索), with women disproportionately affected compared to men.
A large nationwide population-based study from South Korea has identified significant associations between women's reproductive lifespan, hormone replacement therapy (搜索) use, and the risk of developing thyroid cancer (搜索). The findings, presented Saturday at ENDO 2026, the Endocrine Society's annual meeting in Chicago, Illinois, offer new insights into why thyroid cancer occurs more frequently in women than in men.
The research, conducted by scientists from the College of Medicine at The Catholic University of Korea in Seoul, analyzed data from approximately 5.7 million women aged 40 years or older, drawn from the Korean National Health Insurance Service (搜索), which provides universal health coverage.
Study Design and Methodology
The study population consisted of women who participated in breast and cervical cancer screening programs between 2010 and 2011, during which they provided reproductive health details through standardized questionnaires. Participants were followed until a diagnosis of thyroid cancer (搜索), death, or the end of the follow-up period in 2023.
Associations between reproductive factors and thyroid cancer (搜索) incidence were evaluated using Cox proportional hazards regression models. The multivariable analysis was adjusted for a comprehensive set of covariates, including age, smoking status, alcohol consumption, regular physical activity, body mass index, hypertension, diabetes, dyslipidemia, history of cancer, and household income levels.
Key Findings
The researchers determined that approximately 2.4 out of every 1,000 people per year develop thyroid cancer (搜索). A longer reproductive span—the period between menarche and menopause during which women are exposed to endogenous female hormones—was associated with a progressively increased risk of thyroid cancer.
The use of hormone replacement therapy (搜索) (HRT) was also associated with an elevated risk of thyroid cancer (搜索). Notably, a stronger association was observed among women who received HRT for five years or more, suggesting a potential dose-response relationship between exogenous hormone exposure and cancer risk.
"These results show how common life events in women, such as the timing of menopause and use of hormone therapy, may influence cancer risk," said Jinyoung Kim, M.D., Ph.D., assistant professor in the College of Medicine at The Catholic University of Korea. "A woman's reproductive history could be considered in assessing her individual risk to developing thyroid cancer (搜索)."
Clinical Implications
The study addresses a long-standing question in endocrine oncology: why thyroid cancer (搜索) disproportionately affects women. While the sex disparity in thyroid cancer incidence has been well documented, the underlying mechanisms remained unclear. These findings suggest that cumulative exposure to female hormones—both endogenous, through a longer reproductive lifespan, and exogenous, through HRT use—may contribute to thyroid carcinogenesis.
The research underscores the potential value of incorporating reproductive history into individualized thyroid cancer (搜索) risk assessment. For clinicians, this may mean giving greater consideration to factors such as age at menarche, age at menopause, and duration of hormone therapy use when evaluating a woman's thyroid cancer risk profile.
The study's large sample size, nationwide scope, and rigorous adjustment for multiple confounders strengthen the reliability of the findings. However, as with all observational studies, the associations identified do not establish causation, and further research will be needed to elucidate the biological mechanisms linking hormone exposure to thyroid carcinogenesis.