Thyroid cancer risk higher for menopausal women with longer reproductive years
Menopausal women who have 41 or more reproductive years have more than double the risk for developing thyroid cancer compared with women who have 30 or fewer reproductive years, according to study data.
“We simultaneously examined multiple reproductive risk factors and lifestyle factors in relation to the risk of thyroid cancer,” Jane R. Schubart, PhD, associate professor in the departments of surgery, medicine and public health sciences at Penn State College of Medicine, and David Goldenberg, MD, FACS, the Steven and Sharon Baron Professor and Chair, and professor of otolaryngology – head and neck surgery at Penn State College of Medicine, told Healio. “Our key finding was that longer reproductive years increased risk, providing some insights into the higher incidence in younger women during the reproductive years. Our study expands on prior research by simultaneously considering multiple reproductive and hormonal risk factors that cover pregnancy, menstrual cycle, menopause and use of prescription hormones.”
Schubart, Goldenberg and colleagues analyzed data from the Nurses’ Health Study II cohort collected from 1989 to 2013. All self-reported and confirmed cases of thyroid cancer were included in the study. Medical history and health conditions were reported at baseline and updated biennially through 2013. Eating habits and activity status were updated about every 4 years. Participants self-reported menopause status and timing. The findings were published in Women’s Health Issues.
The study included 620 cases of thyroid cancer, with 84% confirmed by pathology reports. Of the cases, 90% were papillary thyroid cancer, 8% follicular and 2% medullary.
Risk for thyroid cancer was more than double for women who had 41 or more reproductive years compared with 30 or fewer reproductive years (HR = 2.2; 95% CI, 1.19-4.06). When age was treated as a continuous variable, there was a significant trend between longer reproductive years and an increased risk for thyroid cancer (P for trend = .006). Age at menopause was not associated with a significant increase in thyroid cancer risk, but there was a significant linear trend between later age at menopause and an increased risk for thyroid cancer when age was analyzed as a continuous variable (P for trend = .009).
“Our key finding was that longer reproductive years increased risk of thyroid cancer, and we found a weak association with various other reproductive factors,” Schubart and Goldenberg said. “This wasn’t surprising, but suggests a synergistic process — that is, multiple genetic, reproductive, environmental and lifestyle factors most likely work together cumulatively to increase risk.”
Parity and the number of months breastfeeding were not significantly associated with an increased risk for thyroid cancer for either premenopausal or postmenopausal women; although age at first delivery was weakly associated with thyroid cancer, those associations did not reach statistical significance. Oral contraceptive use and postmenopausal hormone therapy were also not associated with thyroid cancer risk.
Schubart and Goldenberg said more studies are needed to examine the role estrogen plays in thyroid cancer risk and to better understand the complex biological mechanisms and pathophysiology to explain sex disparity in the development of thyroid cancer.
For more information:
David Goldenberg, MD, FACS, can be reached at firstname.lastname@example.org.
Jane R. Schubart, PhD, can be reached at email@example.com.