Autoimmune thyroid disease: Hashimoto s Thyroiditis is associated with low levels of Vitamin D in adults patients

Abstract

Autoimmune thyroid diseases (AITD) are common autoimmune disorders. Hashimoto’s thyroiditis (HT) is one of the main clinical presentations of AITD and is characterized by lymphocytic infiltration of the thyroid parenchyma. The clinical hallmarks of HT is hypothyroidism, common findings are high serum concentration of thyroid stimulating hormone (TSH) and positive anti-thyroid peroxidase antibodies (ATPO). Evidence suggests that low levels of 25-hydroxy Vitamin D (Vitamin D) may contribute to the development of autoimmune disease; however, the relationship between Vitamin D deficiency and Hashimoto’s thyroiditis is still controversial. The objective of this study is to investigate the association between serum TSH levels, positive ATPO and levels of Vitamin D in healthy and HT patients in the local population. The study was conducted on 190 patients drawn in our clinic between August and November 2016. The mean subject age was 56 ± 17 years old and the male/female ratio was 28 (14.7% male):162 (85.3% female). Pregnant women and patients with abnormal parathyroid hormone levels were excluded. All blood samples were collected in Spring to minimize the impact of seasonal fluctuations of Vitamin D concentrations. We measured TSH, FT4, ATPO and Vitamin D concentrations in healthy and hypothyroids patients. The cut off for positive ATPO was > 37 UI/mL, the normal reference intervals for TSH and FT4 were 0.40 to 4.00 µU/ml, and 1.00 to 1.80 ng/dl, respectively. Deficiency for Vitamin D was defined as serum concentrations below 30 ng/mL. TSH, FT4, ATPO and Vitamin D concentrations were determined using a chemiluminescent microparticle immunoassay (CMIA) on the Advia Centaur XP (Siemens, Germany). Data obtained for all measurements of Vitamin D was analyzed with Welch´s Test. TSH and FT4 in both groups was analyzed using the Mann Whitney U test. A p value < 0.05 represented a significant difference. Data was expressed as mean ± error of the mean (SEM). TSH serum concentrations were significantly increased in hypothyroid patients compared with control patients (4.22 ± 0.51 µU/ml vs 2.20 ± 0.11 µU/ml, p < 0.05). Patients with elevated ATPO had lower concentrations of Vitamin D than the control group (19.13 ± 0.68 ng/mL vs 22.61 ± 0.64 ng/mL, respectively, p < 0.05). FT4 concentrations showed no significant difference between hypothyroid group and control group (1.27± 0.19 vs 1.28 ± 0.11, p < 0.05). Results from the present study support the idea that Hashimoto’s thyroiditis is associated with female gender, positive ATPO, high levels of TSH, and Vitamin D deficiency. We observed that serum Vitamin D concentration is significantly lower in HT patients in comparison to the control group. This suggests Vitamin D deficit may be one of the risk factors for HT development. Importantly, low levels of Vitamin D were observed in control group. We recommend supplementation with Vitamin D in general population.