Thyroid cancer rates on the rise

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Thyroid cancer is on the rise and medical researchers don't know why.

The National Cancer Institute estimates more than 56,000 new cases will be diagnosed this year.

Some researchers think better screening is the reason for the increase.

But other doctors have long believed that obesity, a lack of fruits and vegetables, and radiation exposure play a part in the disease.

Another mystery: why women are almost three times more likely to develop the disease than men.

The good news is that thyroid cancer is usually very curable: The five-year survival rate is 97 percent.

Copyright 2012 KPHO. All rights reserved. CNN contributed to this report.