Study Finds Thyroid Drug Cuts Colon Cancer Risk by 50%

The thyroid hormone replacement drug, levothyroxine, has been found to reduce by half the risk of colorectal cancer. These findings -- the results of research project done by a joint US-Israeli team -- were announced at a meeting of the American Association Cancer Research - Prevention Branch. Colorectal cancer is the second most common cause of cancer deaths in the U.S.

Almost 150,000 new cases are reported each year, and almost 60,000 people are expected to die of colorectal cancer in 2005.

There are some interesting connections:

• Colorectal cancer -- and in particular, colon cancer on the right side of the body, is associated with a higher incidence of thyroid cancer.
• Hypothyroidism (an underactive thyroid) has a negative effect on colon function, which may contribute to increased risk of colorectal cancer

In the research, more than 2000 pairs of patients were studied. In each pair, one patient had been taking levothyroxine to treat hypothyroidism for five years or more, while the control subject was someone of similar age, gender, and other factors, who was not taking levothyroxine.

Even after adjusting for factors protective against colorectal cancer -- engaging in sports and exericse, and eating larger quantitites of vegetables -- the researchers still found that the long-term use of levothyroxine alone resulted in a 50% reduction in colorectal cancer risk.