Epidemiological evidence indicates a significant association between vitamin D deficiency and an increased incidence of autoimmune diseases. With that evidence in mind, a study was done by E. Zold and associates at the Research Laboratory and Academic Clinical Unit of Rheumatology Department of Internal Medicine, University of Genova, Italy.
Dr. Zold and colleagues reported that, during the average 2.3-year follow-up period, 21.7 percent of patients with undifferentiated connective tissue disease (UCTD), an autoimmune disease, and a deficiency of vitamin D metabolites (hormone D) further developed well established autoimmune connective tissue disease (CTD). Patients who progressed into CTDs had lower vitamin D levels than those who remained in the UCTD stage, and UCTD most frequently progressed into rheumatoid arthritis, systemic lupus erythematosus, Sjögren's syndrome, and mixed connective tissue disease. Therefore, vitamin D hormone deficiency is also confirmed in UCTD and might represent a new possible risk factor for the progression into well defined autoimmune rheumatic disease.
Is it "vitamin D" or "hormone D"? Unfortunately, the term vitamin D is an imprecise term, referring to one or more members of a group of steroid molecules (seco-steroids). Vitamin D, also known as cholecalciferol, is mainly generated in the skin of animals when one of the rings of the precursor molecule 7-dehydrocholesterol has been broken by ultraviolet B light (UV-B, sunlight). Vitamin D (hormone D) is thus not a true vitamin, because individuals with adequate exposure to sunlight do not require dietary supplementation. Although vitamin D is consumed in food, dietary intake alone is often insufficient, supplying only 20 percent of the body's requirements. Finally, the liver and kidneys help convert vitamin D to its active hormone forms (vitamin D3 hormone).
In recent years, the discovery of the nuclear vitamin D receptors (VDRs) in the cells of the immune system and the fact that several of these cells produce vitamin D hormone suggested that vitamin D could have immunoregulatory properties. Clearly, topical hormone D analogs are efficient in modulating skin immune response in psoriasis, an autoimmune disease.
In addition, the correction of vitamin D deficiency may be useful in the treatment of B cell-mediated autoimmune rheumatic disorders such as systemic lupus erythematosus. The hormone D immunomodulatory and anti-inflammatory activities might be particularly efficient in rheumatoid arthritis patients and support a therapeutic role in such disease.
--Source: Adapted from "Vitamin D or hormone deficiency in autoimmune rheumatic disease, including undifferentiated connective tissue disease," Maurizio Cutolo, Arthritis Research & Therapy 2008, December 2, 2008. The complete article available online at http://arthritis-research.com/content/10/6/123
