Hypothyroidism linked to liver cancer in women

NEW YORK, 16 may 2009– Women with long-standing hypothyroidism, commonly referred to as an "underactive thyroid," are at increased risk of liver cancer, the results of a new study suggest. By contrast, hypothyroidism is not significantly associated with this malignancy in men.

Hypothyroidism is a condition in which the thyroid gland fails to produce enough thyroid hormone. The thyroid gland normally releases the hormones, T4 and T3, that control metabolism and underproduction may affect all body functions. Risk factors for hypothyroidism include: being older than 50 years of age, exposure of the neck to X-ray or radiation treatments, female gender, obesity and thyroid surgery.

Thyroid hormones are known to be involved in lipid metabolism and fatty acid oxidation and there is evidence linking hypothyroidism with nonalcoholic steatohepatitis - the fatty inflammation of the liver cells -- according to the report in the current issue of Hepatology. However, whether thyroid disorders are associated with liver cancer has been unclear.

To answer this question, Dr. Manal M. Hassan, from the University of Texas M. D. Anderson Cancer Center, Houston, and colleagues compared the occurrence and nature of thyroid disease in 420 patients with hepatocellular carcinoma, the most common type of liver cancer, and a group of 1104 healthy individuals without hypothyroidism.

After accounting for factors that could influence the patients' outcome, such as demographic factors, alcohol use, family history of cancer, and other possible confounders, Hassan's group found that women who had hypothyroidism for longer than 10 years were 2.9-times more likely to develop liver cancer than those without thyroid disease. If the patients also had diabetes and chronic hepatitis virus infection, the odds ratios increased to 9.4-times and 31.2-times, respectively.

As noted, hypothyroidism did not affect the risk of liver cancer in men.

Hyperthyroidism, an "overactive thyroid," also had no impact on the risk of liver cancer in either sex.

"Further studies among different populations are warranted to confirm the association between hypothyroidism and (liver cancer) and to identify the underlying biological mechanisms and the genetic predisposition factors that may contribute to susceptibility to hepatocellular carcinoma development in the presence of thyroid disorders," the authors conclude.

SOURCE: Hepatology, May, 2009.