Thyroid Disorders and Gynecologic Cancers: Is There a Link?

TOPLINE:

The risk of developing gynecologic cancer is lower in women with hyperthyroidism than in those without it, found a large study.

METHODOLOGY:

• Thyroid disease and altered thyroid hormone expression can affect ovulation, endometrial physiology, and estrogen levels, but studies of the association with gynecologic cancer risk have conflicting results.
• This population-based cohort study used data from the Taiwan National Health Insurance Research Database to identify women (mean age, 44 years) who were diagnosed with thyroid disease between January 2000 and December 2018.
• Propensity scores were used to pair 296,872 women with hyperthyroidism and 44,852 with hypothyroidism in a 1:1 ratio with an equal number of individuals without thyroid disorders.
• The cohort was followed up from the date of first diagnosis of hypothyroidism or hyperthyroidism until the diagnosis of gynecologic cancers (endometrial cancer, uterine corpus cancer, and ovarian cancer), death, or the end of 2018.

TAKEAWAY:

• Women with hyperthyroidism had a lower risk for all gynecologic cancers than those without hyperthyroidism (adjusted hazard ratio [aHR], 0.86; P = .0084).
• The risk of developing gynecologic cancer was lower among women with hyperthyroidism aged 20-40 years (aHR, 0.72; P = .0043) but not among those aged > 40 years.
• The reduced risk for gynecologic cancers associated with hyperthyroidism persisted even beyond 6 years of follow-up (aHR, 0.75; P < .001).
• A trend toward a slightly increased risk for gynecologic cancer was observed among women with hypothyroidism; however, the association was not statistically significant.

IN PRACTICE:

The findings may alert oncologists and healthcare decision-makers toward gynecologic cancer trends and prompt further research to understand the mechanism by which thyroid hormone regulates reproductive function, the authors noted.

SOURCE:

This study was led by John Hang Leung from the Ditmanson Medical Foundation Chia-Yi Christian Hospital, Chiayi, Taiwan, and published online in Scientific Reports.

LIMITATIONS:

The study data were obtained from administrative claims databases, so there is a possibility of underestimation or overestimation. Lifestyle factors such as obesity and alcoholism are difficult to measure, so the risk for gynecologic cancers linked to thyroid dysfunction may have been underestimated. Furthermore, because of nonavailability of laboratory data, thyroid hormone status at diagnosis could not be linked to gynecological cancer risk.

DISCLOSURES:

This study was supported by An-Nan Hospital, China Medical University, Tainan, Taiwan. The authors declared no financial interests or conflicts related to the study.

A version of this article appeared on Medscape.com.