Study Shows Thyroid Drug Reduces Risk of Colorectal Cancer

Main Category: GastroIntestinal / Gastroenterology
Article Date: 07 Nov 2005 - 15:00 PDT

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Long term use of L-thyroxin, the principal hormone secreted by the thyroid gland, reduces the risk of colorectal cancer by 50 percent, according to a study presented today at the American Association for Cancer Research's 4th annual Frontiers in Cancer Prevention Research meeting in Baltimore.

Use of L-thyroxin, which is commonly used to treat hypothyroidism, for five or more years was associated with a significantly reduced risk of colorectal cancer (CRC) across study participants of all genders, ages, origins and religions, but reached statistical significance in Jewish females, participants aged 65 and older, and European-American born participants, which were the largest study sub-populations.

Researchers from the Carmel Medical Center, the B. Rappaport Faculty of Medicine, Technion and Clalit Health Services National Cancer Control Center in Haifa, Israel and the University of Michigan Departments of Medicine and Medical Genetics researched the association of long-term use of L-thyroxin as a surrogate measure of hypothyroidism and colorectal cancer using the Molecular Epidemiology of Colorectal Cancer Study (MECC), a population- based case-control study of patients who received a diagnosis of colorectal cancer in northern Israel between 1998 and 2004 and controls matched according to age, sex, clinic, and ethnic group.

Protection against CRC was seen with the use of L-thyroxin in both the right and left colon as well as the rectum. Use of L-thyroxin remained protective after adjusting for patients' use of aspirin and non-steroidal anti-inflammatory drugs (NSAIDs), statin use, first-degree family history of CRC, level of sports activity and degree of vegetable consumption.

"We are pleased that our study showed the effective use of L-thyroxin in patients at most risk for colorectal cancer," according to Dr. Gad Rennert, Carmel Medical Center, Technion and Clalit Health Services National Cancer Control Center, and lead author of the study. "While more research is needed, we believe that knowledge about the role of L-thyroxin could lead to development of a potential preventive treatment against this deadly disease."

"Studies have shown that right-sided colon cancer is associated with an increased risk of thyroid cancer, and a predisposition to thyroid cancer is a well described feature of Familial Adenomatous Polyposis, a disease that is marked by the formation, especially in the colon and rectum, of numerous benign polyps which typically become cancerous if left untreated," said Dr. Stephen Gruber from the University of Michigan. Hypothyroidism is known to impair colonic motility and transit time, suggesting its relation to colon cancer.

The use of L-Thyroxin was recorded through structured, in-person interviews with participants as was all other medication use, for five years or more. Use of L-thyroxin was verified through computerized prescription records. Researchers based the results on 2,102 matched pairs of participants.

Founded in 1907, the AMERICAN ASSOCAITION FOR CANCER RESEARCH is a professional society of more than 24,000 laboratory, translational, and clinical scientists engaged in all areas of cancer research in the United States and in more than 60 other countries. AACR's mission is to accelerate the prevention and cure of cancer through research, education, communication, and advocacy. Its principal activities include the publication of five major peer- reviewed scientific journals: Cancer Research; Clinical Cancer Research; Molecular Cancer Therapeutics; Molecular Cancer Research; and Cancer Epidemiology, Biomarkers & Prevention. AACR's Annual Meetings attract nearly 16,000 participants who share new and significant discoveries in the cancer field. Specialty meetings, held throughout the year, focus on the latest developments in all areas of cancer research.

Hypothyroidism and the Risk of Colorectal Cancer
Abstract # 2115 Gad Rennert, Carmel Medical Center, Technion and Clalit
Health Services National Cancer Control Center, Israel

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