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CLEVELAND (WJW) – It’s one of the fastest-growing cancers that often goes undetected.

An estimated 20 million Americans have some form of thyroid disease. According to the American Thyroid Association, up to 60% are unaware.

The new Browns defensive coordinator Jim Schwartz opened up about his battle with thyroid issues Wednesday and said it forced him to temporarily step away from the game he loves.

“My thyroid went kaput a couple of years ago,” said Schwartz. “It took the greater part of about 18 months to get my numbers to where they needed to be. It was a very difficult decision, but I had to step away.”

Danielle Herman, a 26-year-old medical student at Case Western Reserve University, was one of the millions unaware of her body’s struggle with the disease.

“I actually didn’t think anything was wrong,” she said.

Herman said her father’s advocacy about the importance of getting annual physical exams led to the discovery of a stunning thyroid cancer diagnosis.

“I was really shocked. I had learned about thyroid cancer in my first year of medical school, but I hadn’t learned how common it is in young women,” said Herman.

Her doctor noticed her thyroid was asymmetrical and felt a lump. Further testing and surgery earlier this month revealed cancer. Herman is a patient of Dr. Joyce Shin, an endocrine surgeon at the Cleveland Clinic.

“Thyroid cancer is now the fastest-growing cancer in women,” said Shin. “I would say on average one out of five women will have something growing in the neck, in the thyroid. The older we get as women and even in men, the more nodulus we will develop.”

She says the increase could be attributed to the rise in medical imagining for other issues able to spot the disease. Herman encourages others to check for warning signs.

“The importance of a neck self-exam, looking and feeling your neck,” she said. “I think, as young women, we’re taught how to do breast self-exams, but I’ve never even heard of doing a neck self-exam.”

Most thyroid cancers are responsive to treatment, according to the American Thyroid Association. However, the causes are often unknown and the condition can be lifelong.

“I didn’t expect to deal with something like this at 26,” said Herman. “Now having dealt with it and finding some community, I realize a lot of women in their 20s and 30s are dealing with it and in that sense, it’s been nice to find community.”