Hepatitis is an inflammation of the liver tissue. It can have a number of causes, ranging from alcohol and certain drugs to an autoimmune disease, but the most common cause are hepatitis viruses. The hepatitis C virus (HCV) causes both acute and chronic infection. Acute hepatitis C lasts anywhere from a few weeks to six months, often has no symptoms, and doesn’t require specific treatment.
Types of thyroid disease
Thyroid glands produce hormones that influence almost all of the metabolic processes in the human body. The most common thyroid problems happen due to abnormal production of these hormones:
- Either insufficient production, a condition that’s called hypothyroidism
- Or overproduction, which results in an excessive quantity of thyroid hormones and is called hyperthyroidism
These conditions have different causes and can strike due to environmental factors such as exposure to excessive amounts of iodide or lithium, or as a result of autoimmune disease.
In autoimmune diseases, the body attacks itself. Immune cells produce antibodies, proteins that normally recognize and attack pathogens like bacteria and viruses, but in the case of autoimmune diseases, they attack healthy tissue and cells. In autoimmune thyroid diseases, thyroid tissue that is under attack slowly dies off and that results in lower hormone production.
Other than abnormalities in hormone production, another problem is thyroid cancer. According to a report issued by the Nation Cancer Institute, over 56,000 new cases of thyroid cancer are reported in the US each year. By far the most common type is papillary thyroid cancer. It’s three times more common in women than in men.
How is hepatitis C linked to thyroid disease?
One of the main problems with a hepatitis C infection is that it’s much more than a condition affecting the liver. The term HCV-syndrome refers to a complex of HCV-driven diseases that include hematologic, renal, rheumatic and endocrine diseases. In addition to that, it is both a hepato- and lymphotropic virus, meaning it attacks both hepatocytes (the liver cells) and B-lymphocytes (a type of immune cell that produces antibodies). It does so by recognizing a specific protein that is present on the surface of both of these types of cells.
While our immune system helps fight pathogens like bacteria and viruses, it also helps protect against cancer. With other contributing factors, its influence on the immune system leads to hepatitis C having an "oncogenic potential", meaning that a number of malignant cancers have been linked with HCV infection, particularly B-cell non-Hodgkin’s lymphoma, pancreatic cancer and papillary thyroid cancer.
There are two ways in which a hepatitis C infection can lead to thyroid disease. One is the effect of the virus itself, through attack on thyrocytes and on the immune system, contributing to autoimmune response and oncogenic potential. The other is through therapy taken for HCV, namely interferon-alpha (IFN-α).
Autoimmune thyroiditis
Autoimmune thyroiditis (AT) includes a group of thyroid diseases characterized by a chronic inflammatory response, self-directed against the thyroid gland. It can lead to both hyperthyroidism and hypothyroidism. The most common types are Hashimoto’s thyroiditis (hypothyroidism) and Graves’ disease (hyperthyroidism).
Antibodies through which cells involved in the immune system specifically recognize thyroid glands as their target are called antithyroid antibodies. As such, they can be used as markers for autoimmune thyroiditis. By testing HCV-infected patients who haven’t been treated with interferon for these markers, researchers showed that abnormally high levels of antithyroid antibodies ranged anywhere from two percent to up to 48 percent. These differences have to do with the fact that probability of HCV-induced thyroid problems largely depend on other factors such as sex, age, ethnicity and where you live.
Thyroid dysfunction associated with type I Interferon therapy
Type I interferons are proteins used in the therapy of several diseases, including hepatitis B and C and multiple sclerosis, as well as some types of cancers. They have a broad spectrum of effects including antiviral, antibacterial and immuno-modulating effect, meaning that they change responses of immune cells. Immune stimulation can activate or amplify multiple aspects of the immune response, but that can sometimes also induce or exacerbate autoimmune disease.
Side effects of interferon therapy are not uncommon and can vary from less serious effects like nausea and headache to serious problems like a range of autoimmune disorders. Thyroid disorders develop in one to 35 percent of interferon-treated patients, and include both autoimmune and non-autoimmune thyroiditis, although autoimmune appears to be much more common. Even though this problem has been known for decades, the exact mechanism of thyroid damage still remains a mystery.
Conclusion
Hepatitis C is a virus that can cause serious liver inflammation, but it also affects other organs in the body. Thyroid gland problems such as thyroid gland cancer as well as hypothyroidism and hyperthyroidism have been linked to HCV infection as well as interferons used for its treatment. Hyper- and hypothyroidism can often go undetected in first phases, so if you have hepatitis C regular screening for thyroid cancer as well as monitoring of thyroid hormones is recommended.
- Photo courtesy of SteadyHealth