Thyroids and Fibroids: What’s the Connection?

Thyroids and Fibroids: What’s the Connection?

Thyroids and fibroids don’t just sound alike; they may be linked in other, more significant, ways. A recent study from Seoul, South Korea’s Inje University College of Medicine explores this relationship, specifically the potential connection between uterine fibroids and different types of thyroid disease. Read about their findings, and what they could mean for your fibroid diagnosis. 

What the Researchers Did

Using data from South Korea’s National Health Insurance Registry, the research team identified patients who underwent uterine myomectomy from 2009-2020. All women surveyed were between the ages of 20-50, and a total of 181,419 patients were included across the uterine fibroid (myomectomy recipients) and control (women without fibroids) groups. 

The team measured different types of thyroid disease among the fibroid and control groups over a multi-year period. Specific types of benign thyroid conditions measured included:

  • Hyperthyroidism (overactive thyroid), 
  • Hypothyroidism (underactive thyroid),  
  • Autoimmune thyroid disease, 
  • Goiters, and 
  • Nontoxic single thyroid nodules. 

What They Found and What It Means

Although both the fibroid and control groups showed nearly identical rates (0.6%) of hypothyroidism and hyperthyroidism, rates of non-toxic nodules and goiters, as well as overall thyroid disease, were much higher among the fibroid patients

“The results suggest that women with uterine fibroids have an increased risk of thyroid goiters and thyroid nodules,” write study authors. “Although the mechanism is not well known, estrogen and iodide might be a link between uterine fibroids and thyroid goiters and nodules. Future studies that prospectively follow women with uterine fibroids across a lifetime are needed.”

Related Studies 

The link between thyroid issues and uterine fibroids has been studied for years. One previous study found that nearly 18% of women with thyroid nodules also had uterine fibroids. A growing body of research links the development of thyroid nodules to estrogen production. Data from the Society for Endocrinology also indicate an association between estrogen production and thyroid cancer. Their findings are reinforced by lower rates of thyroid cancer and similar diseases before puberty and after menopause when estrogen production is at its lowest. 

Are Thyroid Goiters and Nodules Dangerous?

About 90% of thyroid nodules turn out to be benign, but it’s prudent to eliminate the possibility of cancerous cells through ultrasound, biopsy, or other measures. A goiter is simply an enlarged thyroid gland. Goiters are also generally benign, though they can dramatically change appearance. Consult with your doctor to schedule appropriate testing. Treatment for goiters and nodules may include surgery, medications, radiofrequency ablation (RFA), or just watchful waiting to determine size fluctuation. 

The Bottom Line 

The link between thyroid growths and uterine fibroids has been clearly established and is most likely the result of excess estrogen. If you have fibroids and a family history of thyroid conditions, especially thyroid cancer, even if you aren’t experiencing symptoms, consider talking to a primary care physician or your OB/GYN for an endocrinology referral. 

*Yuk, J., Min Kim, J. (2022, April 2). Uterine Fibroids Increase the Risk of Thyroid Goiter and Thyroid Nodules. Scientific Reports.

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