Until recently, thyroid cancer was the most rapidly increasing cancer in the U.S., due largely to improved detection. Because this cancer has a relatively low mortality rate, it is not uncommon for gynecologists to encounter a thyroid cancer survivor in their practice.
Some thyroid cancer survivors may experience gynecological issues as a result of treatment or the cancer itself. Improving or bolstering knowledge of thyroid cancer and complications related to its treatment can help OBGYNs better care for these patients.
Thyroid Cancer and Reproductive Complications: What's the Link?
The American Cancer Society estimates that 32,130 women were diagnosed with thyroid cancer in 2021 alone. Women are three times more likely than men to develop thyroid cancer, a disease that is typically diagnosed at a younger age than many other cancers — usually under age 50. The majority of thyroid cancers are papillary cancers, which tend to grow very slowly. Even when papillary thyroid cancer has spread to the lymph nodes, it typically responds well to treatment and is rarely fatal.
For this reason, physicians can expect to care for young female thyroid cancer survivors, a population with its own complications, risks and healthcare needs. Specifically, research published in the Journal of Cancer Survivorship suggests that female thyroid cancer survivors have higher rates of certain gynecological conditions, including cervicitis and endocervicitis, menstrual irregularities, early menopause, and ovarian cysts. The increased risk persists for one to five years after cancer treatment.
The study also found that thyroid cancer survivors who became pregnant during that time had an increased risk of certain complications, including gestational diabetes. Study participants who became pregnant also had increased rates of miscarriage or spontaneous abortion in the first year after radioactive iodine treatment.
Radioactive Iodine Treatment and Gynecological Issues
Some of the risks and complications identified in the Journal of Cancer Survivorship study are linked to radioactive iodine treatment, a common treatment for thyroid cancer. Because the thyroid absorbs almost all of the iodine in the body, radioactive iodine (also known as I-131) can be an effective approach to treating any remaining cancerous tissue that is not removed during surgery. Radioactive iodine destroys the thyroid gland — along with any cancerous cells — causing few other lasting side effects.
That said, some gynecological complications have been observed following the use of radioactive iodine therapy. Although radioactive iodine is associated with a low sperm count and other fertility issues in cisgender men who receive it, cisgender women with thyroid cancer may also experience gynecological and reproductive issues after radioactive iodine therapy, reports the American Cancer Society. In particular, radioactive iodine has been linked to irregular menstrual periods for up to a year after treatment. In addition, most physicians recommend that women who have received radioactive iodine therapy wait at least six months to a year after treatment before becoming pregnant.
Although some studies suggest that pregnant women who underwent radioactive iodine therapy may be at higher risk of having a miscarriage or spontaneous or induced abortion in the first year after treatment, there is no evidence of a longer-term risk. Indeed, no ill health effects have been found in children born to parents who received radioactive iodine therapy in the past. A good rule of thumb may be to ask a thyroid cancer survivor to delay conception by about a year after treatment with radioactive iodine.
Other Considerations for OBGYNs
Although most gynecologic and reproductive concerns appear to be directly linked to radioactive iodine therapy, others may be present in patients who have survived thyroid cancer, regardless of their treatment. For example, the Journal of Cancer Survivorship study found more than a two-fold increased risk of diabetes or abnormal glucose tolerance during pregnancy, childbirth and the puerperium in women who have had thyroid cancer. This includes gestational diabetes and complications of type 2 diabetes during pregnancy. These risks may be elevated further in a thyroid cancer survivor who is overweight or obese.
This connection could signal the need for careful observation and care of thyroid cancer survivors during early pregnancy, as well as screening for gestational diabetes.
The establishment of a link between radioactive iodine therapy for thyroid cancer and increased gynecological risks is illuminating for both gynecologists and oncologists, but more research is needed on the possible reproductive health effects of other thyroid cancer treatments. Researchers do not yet know how or if the suppression of thyroid-stimulating hormone affects genital and reproductive outcomes in women who have had thyroid cancer.
Providing Exceptional OBGYN Care to Thyroid Cancer Survivors
The good news is that many patients who have had thyroid cancer are still able to have healthy pregnancies and normal deliveries. However, these patients may have questions about monitoring for diabetes and other conditions during pregnancy. OBGYNs who provide care to female thyroid cancer survivors can help support these patients in a number of ways.
First, conduct a thorough medical history with every patient to reveal any past or current health issues, including any past cancer or cancer treatment. That knowledge can help guide decision-making, particularly when it comes to questions surrounding fertility, conception and pregnancy.
Second, by encouraging patients who have undergone treatment for thyroid cancer to wait a year or more before trying to conceive, OBGYNs can help ensure these patients are more likely to experience a healthy pregnancy and delivery, regardless of past cancer treatment. Women who have been diagnosed with thyroid cancer in the past may also benefit from close observation during pregnancy, as well as screening for gestational diabetes.
OBGYNs should reassure patients who have had thyroid cancer about their gynecological health while acknowledging the possible risks that may accompany radioactive iodine treatment. In doing so, you can build patients' trust and optimize their care.
