Genetic intestinal condition increases risk of thyroid disease, cancer

Recent research seems to confirm the growing consensus that an inherited intestinal polyp condition may increase the risk of thyroid disease.

A study published in the journal Hereditary Cancer in Clinical Practice found that 6 percent of surveyed patients with familial adenomatous polyposis (FAP) experienced thyroid cancer. Another 9 percent suffered from or had experienced a thyroid disease like Hashimoto's thyroiditis, thyroid cysts or goiter.

Researchers noted that the rate of thyroid cancer among these patients is consistent with previous scientific inquiries, which indicate that people with FAP have a higher likelihood of being diagnosed with a thyroid carcinoma.

The lifetime risk of thyroid cancer in the U.S. is approximately one in 111, or just under 1 percent, according to the National Cancer Institute.

Among patients with FAP, prior research has found that the rate of thyroid cancer tends to be significantly higher, often between 1 and 15 percent, depending on the study.

FAP is a genetic disorder in which polyps begin growing in the stomach and large intestine, sometimes as early as in adolescence. Without treatment, these polyps will become cancerous, the National Institutes of Health (NIH) states.

Approximately 1 percent of all cases of colorectal cancer are related to FAP in some way, according to the NIH. The organization adds that the average age at which people with FAP develop colorectal cancer is 39.

In the new study, researchers noticed that certain participants with FAP had suffered or were suffering from other thyroid diseases as well.

Some had Hashimoto's thyroiditis, which is inflammation of the thyroid gland that can cause hypothyroidism. Others had goiter, a condition most commonly caused by iodine deficiency. The team noted that this latter condition is also known to be caused by cystic growth.

Researchers concluded that thyroid cancer and diseases of the gland are more likely to occur among those with FAP.

The NIH estimates that between one in 7,000 and one in 22,000 Americans has FAP.