Longer lifetime exposure to female hormones may increase a woman’s risk of thyroid cancer, according to research presented Saturday at the Endocrine Society’s annual meeting ENDO 2026 in Chicago, Illinois. This study suggests that reproductive and hormonal factors may be involved in thyroid carcinogenesis.
Thyroid cancer occurs more frequently in women than men, but the reason for this increase remains unclear. Scientists at the Catholic University of Korea School of Medicine in Seoul designed a study to find out why. They conducted a nationwide population-based survey of approximately 5.7 million women over the age of 40 using data from the Korea National Health Insurance Corporation, a program that provides universal health coverage.
The study population participated in a breast and cervical cancer screening program between 2010 and 2011 and shared reproductive health details using a standardized questionnaire. Women were followed until thyroid cancer diagnosis, death, or end of follow-up in 2023. Associations between reproductive factors and thyroid cancer incidence were assessed using Cox proportional hazards regression models. Multivariate models were adjusted for age, smoking status, alcohol intake, regular physical activity, BMI, hypertension, diabetes, dyslipidemia, history of cancer, and household income level.
Scientists have found that about 2.4 in 1,000 people develop thyroid cancer each year. We found that the risk of thyroid cancer gradually increases with longer reproductive years. Use of hormone replacement therapy (HRT) was also associated with increased risk of thyroid cancer, with a stronger association observed among women who took HRT for more than 5 years.
These results show how common life events in women, such as the timing of menopause and the use of hormone therapy, can influence cancer risk. A woman’s reproductive history may be considered when assessing an individual’s risk of developing thyroid cancer. ”
Jinyoung Kim, MD Ph.D. Assistant Professor, Catholic University of Korea, School of Medicine
