Myth: Thyroid cancer occurs less in men than in women

By Jessica Saenz

Women are three to four times more likely than men to be diagnosed with thyroid cancer. This disparity has led to a widespread belief that women develop thyroid cancer more than men. But recent research suggests that thyroid cancer occurrence might be more equal in men and women than previously believed.

"Many people will live years and decades with thyroid cancer. We want to make sure men know that they are at risk for thyroid cancer, and it's not necessarily a disease of women," says Victor Bernet, M.D., a Mayo Clinic endocrinologist.

Dr. Bernet and Ashish Chintakuntlawar, M.B.B.S., Ph.D., a Mayo Clinic medical oncologist and researcher who specializes in advanced thyroid cancer, discuss the current understanding of sex disparities in thyroid cancer and why individualized assessment of each person is best.

The cause of sex disparities in thyroid cancer diagnosis is unclear.

Cancer experts don't know why thyroid cancer diagnosis is so much higher in women than in men.

Some studies have explored the idea that women are more likely to seek medical care than men and are, therefore, more likely to be diagnosed with thyroid cancer — particularly small, asymptomatic papillary thyroid cancers. Dr. Bernet says this could be one contributing factor. "This has made it look like women are more at risk, when in reality, it may be that the gender risk is similar," he says.

Improvements in imaging technology have also led to an increase in the detection of microcarcinomas — papillary thyroid tumors smaller than 1 centimeter — especially in women. Papillary thyroid cancer is the most common type of thyroid cancer and is typically less aggressive. This type of thyroid cancer usually does not cause symptoms and is often detected incidentally in unrelated exams.

"Gender differences, where thyroid cancer is three to four times more commonly diagnosed in women, are true for the smaller sized thyroid cancers and especially true for papillary thyroid cancers that are less than two centimeters in size," says Dr. Chintakuntlawar.

Though it has been widely believed that female sex hormones play a role in thyroid cancer development, there's some disagreement about whether they contribute to higher rates of thyroid cancer in women. "There are studies that say estrogen can affect the growth of thyroid cells. And there are conflicting studies that say hormones like estrogen have no effect on the development of thyroid cancer," says Dr. Chintakuntlawar.

Aggressive thyroid cancers affect men and women almost equally.

Dr. Chintakuntlawar says that in advanced or more aggressive thyroid cancers, the gender difference becomes less obvious. "The incidence tends to be equal in men and women," he says. Advanced thyroid cancers are cancers that are large, recurrent or have spread beyond the thyroid.

A rare type of thyroid cancer called medullary thyroid cancer can run in families. About 25% of medullary thyroid cancers are considered hereditary, and they are usually associated with a genetic condition called multiple endocrine neoplasia, type 2 (MEN2), according to the National Cancer Institute. MEN2 is a rare genetic disorder that can be inherited regardless of sex.

Dr. Chintakuntlawar says most thyroid cancer cases are not linked to inherited genetic mutations or other risk factors. Since most people are unaware of their genetic risks, it's best to get genetic counseling and testing if you know thyroid cancer runs in your family. "Once you know you carry or don't carry the mutation, then you can streamline your future healthcare based on that."

Sexes aside, specialized and individualized care is best for thyroid cancer.

Thyroid cancer should always be evaluated by healthcare professionals who specialize in treating it. "I cannot overemphasize this. It is extremely important to get treated at a center of excellence that specializes in thyroid cancer — both for early-stage and advanced thyroid cancers," says Dr. Chintakuntlawar. "This disease tends to be unique to each person, and the experience and the coordination needed between endocrinologists, surgeons, medical oncologists and radiation oncologists has to be seamless to avoid over- or under-treatment."

Some thyroid cancers require immediate treatment. However, in many cases, thyroid tumors can remain small without causing symptoms or complications for decades. "There's a debate about microcarcinomas and how much we help people by catching them super early because this has led to overdiagnosis, or diagnosis at a time when treatment isn't needed. You want to diagnose cancer at a point where you can impact the patient's outcome," says Dr. Bernet.

Thyroid cancer treatment can have long-term side effects and complications, including the need for lifelong hormone replacement medications, low levels of calcium (hypocalcemia), low levels of parathyroid hormone (hypoparathyroidism) and dry mouth. And because the structures around the thyroid are closely confined, surgery can sometimes damage the trachea, parathyroid glands and larynx.

If you are diagnosed with thyroid cancer, your care team might recommend active surveillance, which involves monitoring your cancer through exams and tests. Active surveillance is best managed by thyroid cancer specialists who can identify changes that might signal a need for treatment. This approach can help people avoid or delay some of the long-term side effects of thyroid cancer treatment and preserve quality of life.

"The vast majority of people will not die from papillary thyroid cancer," says Dr. Bernet. "Some patients present with more advanced papillary thyroid cancer, and things are a little bit more challenging. But for the most part, we see patients for many years and decades with individualized care and follow-up, and people can do exceedingly well."

Learn more

Learn more about thyroid cancer and find a clinical trial at Mayo Clinic.

Join the Thyroid Cancer Support Group on Mayo Clinic Connect, an online community moderated by Mayo Clinic for patients and caregivers.

Also read these articles:

• Unleashing CAR-T cell therapy to destroy solid tumors in thyroid cancer
• You survived thyroid cancer. What’s next?
• Dear Mayo Clinic: Thyroid nodules, cancer and treatment
• What you should know about thyroid cancer in adolescents, young adults