Introduction: Vitamin D is a hormone that acts through the Vitamin D receptor (VDR) not only on the skeletal system but on a great number of target tissues, including thyroid gland. In recent years the association of vitamin D with autoimmune thyroid diseases (AITD), has been suggested.
VDR gene polymorphisms had been associated with an increased risk of AITD. In addition a recent meta-analysis showed that AITD patients had lower level of 25-hydroxyvitamin D. However some studies have not confirmed the association between vitamin D levels and AITD. Furthermore, data on the effects of vitamin D in thyroid hormones and TSH serum levels are very poor.
The aim of our study was to evaluate the association of vitamin D levels with thyroid function and positivity for thyroid antibodies.
Material and methods: PORMETS is a nationwide, cross-sectional study in Portugal comprising a sample of 4095 adults. Five hundred participants were randomly selected to be included in the present study. A fasting venous sample was collected and serum calcium, PTH, 25-hydroxyvitamin D [25(OH)D], TSH, FT4, FT3 and thyroid antibodies were measured.
Results: Our study included 286 women and 214 men with a mean age of 53.4 years.
Free thyroxine (FT4), free triiodothyronine (FT3), TSH and thyroid antibody levels did not present any significant linear correlation with 25(OH)D levels.
After adjustment for sex and age, TSH, FT4 and FT3 levels did not present any significant association with 25(OH)D levels or with low vitamin D status.
Logistic regression analysis did not show any significant association of low vitamin D status with thyroid antibodies positivity, even after adjustment for several possible confounding variables.
Conclusion: Our results do not confirm the association of vitamin D levels with thyroid function and positivity for thyroid antibodies.
20 - 23 May 2017
European Society of Endocrinology