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artículos de investigación enzyme 1-alpha-hydroxylase has been detected in various tissues and 1,25 (OH)2D3 is produced extra-renally via paracrine action, suggesting that vitamin D could have many functions outside the skeletal system including roles in endocrine diseases21 23. 1,25 (OH)2D3 is an important immune system regulator, modulating B and T lymphocyte functions24,25. The immune-modulatory function of active vitamin D is attributed to its effects on innate and adaptive system cells. 1,25 (OH)2D3 inhibits T cell proliferation via IL-2, IFN-ƴ and IL-1726,27. Studies suggest 1,25 (OH)2D3 may prevent development or attenuate signs of autoimmune, 614 inflammatory, infectious and cardiac diseases as well as cancer8,22,24,28. In recent years, researchers have focused on understanding the non-calcemic role of vitamin D on the immune system and, especially, T cell-mediated immunity. Tamer et al.29 found low vitamin D levels in adult patients with HT and high prevalence of vitamin D insufficiency. In a similar study, Kivity et al.12 found a higher ratio of vitamin D deficiency (< 10 ng/mL) in patients with HT compared with the controls. Nasrin Mansoruni et al.30 had similar results. In a study conducted on a childhood age group, Çamurdan et al.31 found a higher frequency of vitamin D deficiency in the HT patients than controls. In our study, the ratio of vitamin D deficiency was higher in the patient group than the control group. To the best of our knowledge, our study is the second study on childhood age patients involving children with the autoimmune disease HT. Our study indicated that vitamin D deficiency rate is high among children with HT. In our study, vitamin D andanti-TPO levels were negatively correlated, although without statistical significance. Anti-TPO and anti-TG appear independent of vitamin D pathophysiologically. However, the association between vitamin D deficiency and anti-TPO shown in previous studies appearsto be related only to severe deficiency of vitamin D12,32-35. In one study where vitamin D deficiency was defined as levels < 20 mg/dL, there was no associationbetween vitamin D and anti-TPO. Patients with HT who are euthyroid and asymptomatic at the time of diagnosis develop hypothyroidism within a number of years3,14,36,37. An interesting finding in our study was that all HT patients with PHT had low levels of vitamin D. Similar to our results, previous studies reported lower vitamin D levels in patients with PHT Hypovitaminosis D in Children - E. Sönmezgöz et al than controls, and a positive correlation between vitamin D deficiency and TSH levels. However, those studies did not report a significant difference between hypothyroidism groups with regard to the association between vitamin D levels and TSH. This condition may be explained by euthyroidism in patients with HT at the time of diagnosis and disturbance of thyroid function tests over a long period of time. Currently, vitamin D is recognized as necessary for optimal health. Apart from calcium and phosphorus metabolism, vitamin D may play an important role in the pathogenesis of various autoimmune, degenerative and inflammatory diseases and cancer15,22. However, there is no consensus on the optimal serum vitamin D concentrations for bone health and prevention of extra-skeletal diseases6,38,39. Currently, serum vitamin D levels above 30 ng/mL are considered the most beneficial for maintenance of bone health. However, data regarding the recommended daily amount of vitamin D necessary to achieve these levels is contradictory8,38. Vitamin D levels are influenced by various factors such as geographic differences, seasonal changes, time spent outdoors and traditional clothing habits. Low levels of vitamin D in some autoimmune and chronic diseases may be attributed to insufficient outdoor activities due to present diseases (i.e., SLE, MS, RA, cancer), malabsorption (inflammatory bowel diseases) and long-term use of corticosteroids5,8,40,41. Factors such as these that could affect vitamin D levels are unlikely in HT subjects. Our study had several limitations. First, statistical evaluation regarding feeding and clothing habits and time spent outdoors was not possible. Second, a statistically significant difference with regard to age was observed between the patients and the controls who visited our outpatient clinic for routine check-ups. In conclusion, vitamin D deficiency is common in children with HT. The correlation between vitamin D and anti-TPO appears related to severe vitamin D deficiency. Although vitamin D levels are influenced by various factors, studies from different geographical regions found higher rates of vitamin D deficiency in many autoimmune diseases compared with controls. Our findings suggest vitamin D may have a significant role in the pathogenesis of the autoimmune disease HT. Rev Med Chile 2016; 144: 611-616


Mayo 2016
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