Menstrual and reproductive factors, exogenous hormone use, and risk of thyroid carcinoma in postmenopausal women

Abstract

To investigate the association of reproductive factors and hormone therapy, including type of hormone therapy, with risk of thyroid cancer in postmenopausal women. We assessed these associations with risk of incident thyroid cancer in a cohort of 145,007 postmenopausal women enrolled in the Women's Health Initiative. Over 12.7 years of follow-up, 296 cases of thyroid cancer were identified, including 243 with papillary thyroid cancer. Cox proportional hazards models were used to estimate hazard ratios and 95 % confidence intervals for exposures of interest. In both age-adjusted and multivariable-adjusted analyses, menstrual and reproductive factors including age at menarche, age at menopause, age at first birth, age at last live birth, parity, duration of breastfeeding, miscarriages, stillbirths, hysterectomy, bilateral oophorectomy, and use of oral contraceptives were not associated with risk of all thyroid cancer or papillary thyroid cancer. In addition, ever use of menopausal hormone therapy, current or former use, duration of use, and type were not associated with risk. We found little support for associations of reproductive or hormonal factors with risk of developing thyroid cancer. Importantly, our study showed no association of type of hormone therapy used with thyroid cancer risk.