Melatonin is a hormone produced by the pineal gland at the base of your brain. Its production and release is enhanced when you are in darkness and suppressed when you are exposed to bright light. By stimulating receptors in specific areas of your brain, melatonin helps establish your day-night rhythm and determine your sleep cycles. Melatonin also acts as an antioxidant, an antiinflammatory, a stimulator of bone growth and an immune-regulating hormone.
Autoimmune disorders occur when your immune system produces antibodies directed against your own tissues. When these so-called autoantibodies attack your cells or tissues, they trigger an inflammatory response that can cause widespread damage. Components of this abnormal immune response include white blood cells and the inflammatory chemicals they produce, such as cytokines and prostaglandins.
Neuroendocrine Immune System
Your immune system is regulated by a multitude of internal and external forces. An imbalance between your immune system and several of hormones -- such as melatonin, cortisol, vitamin D and sex hormones -- is one of the primary driving forces behind a variety of diseases, including many autoimmune disorders. The interaction between your hormones and immune system is called the neuroendocrine immune system, or NEI.
Some hormones involved in the NEI heighten your immune response, while others help suppress it. Under normal circumstances, these opposing forces allow your immune system to efficiently address threats without causing injury to your own tissues. Cortisol and vitamin D have been shown to exert suppressing effects on the immune response, making them desirable agents for treating conditions wherein your immune system is overactive, such as autoimmune disorders.
Despite melatonin’s antioxidant properties, it has demonstrated a tendency to stimulate inflammation in people with certain autoimmune disorders. A study published in the October 2007 issue of the "British Journal of Clinical Pharmacology" demonstrated that rheumatoid arthritis actually worsened in study subjects who took melatonin. This finding surprised and disappointed the study’s authors, who thought supplemental melatonin might benefit people with autoimmune diseases. However, these results mirror more recent research published in May 2014 in the "Journal of Immunology Research," which confirms that high levels of melatonin seem to worsen rheumatoid arthritis by stimulating immune cells to release inflammatory cytokines.
The interactions of the NEI components are complex. Some previously observed properties of melatonin, such as its antioxidant activity, have not been borne out in all research studies. This has led some experts to recommend that you not use melatonin if you have an autoimmune disease, since it could aggravate your already overactive immune system and lead to worsening of your symptoms. Always talk with your doctor before taking any supplement for an autoimmune disease, as it may be harmful or interact with your medications.