Endocrine Abstracts

Introduction

The main role of vitamin D is regulating bone metabolism, but over the past years, the importance of vitamin D in non-skeletal actions has been studied. Vitamin D deficiency is very common in our environment. This deficit has been associated with higher risk of many chronic diseases, such as osteoporosis, hypertension, diabetes and even obesity. Recent evidence has demonstrated an association between low vitamin D status and autoimmune thyroid diseases such as Hashimoto’s thyroiditis. Moreover, vitamin D plays a significant role in modulation of the immune system, enhancing the innate immune response while exerting an inhibitory action on the adaptive immune system.

Objectives

To evaluate whether there is a higher prevalence of vitamin D deficiency among patients with Hashimoto’s hypothyroidism and whether it is correlated with laboratory parameters such as TSH, free T4 or the levels of anti-peroxidase (TPO) and anti-thyroglobulin antibodies.

Methods

The medical history and laboratory tests of 200 patients with autoimmune hypothyroidism treated in our hospital (Hospital Clínico Lozano Blesa, in Zaragoza; Spain) were collected for this study. Vitamin D levels under 30 ng/ml were considered to be vitamin D deficiency. Student’s T test was used for statistical analysis.

Results

Vitamin D deficiency was frequent among hypothyroid patients (42.6%). In addition, higher mean values of anti-tiroglobulin antibodies have been obtained in patients with low vitamin D (235.14 IU/ml versus 102.32 IU/ml, P = 0.011), as well as higher mean values of TSH (20.45 mU/l vs 8.45 mU/l P = 0.028). There were no differences between the FT4 values or anti-TPO antibodies of both groups.

Discussion and conclusion

A high prevalence of vitamin D deficiency was found among patients with Hashimoto’s thyroiditis. Moreover, those with higher TSH and/or higher anti-thyroglobulin antibody levels had lower vitamin D levels. Various studies have recognized the pleiotropic roles of vitamin D, which have suggested a beneficial role of this vitamin in the management of thyroid disease. However, only an ambiguous causal relationship has been reported to date, so the potential of vitamin D as a treatment in thyroid diseases remains debated. Long-term, randomized controlled trials are required to determine whether patients with low vitamin D levels are at increased risk of developing autoimmune thyroiditis, and to provide insight into the efficacy of vitamin D as a therapeutic agent for this disease.