Endocrine Abstracts

Context: Vitamin D deficiency has been identified as a risk factor for a number of autoimmune diseases including type 1 diabetes and multiple sclerosis.

Objective: We hypothesized that low levels of vitamin D are related to the early stages of autoimmune thyroid disease.

Design: Two case-control studies were performed. Study A: cases were subjects from the Amsterdam AITD cohort (euthyroid women who had 1st or 2nd degree relatives with overt AITD) who at baseline had normal TSH and no thyroid antibodies; controls were healthy women examined at the same time period. Study B: cases and controls were subjects from the Amsterdam AITD cohort who at baseline had normal TSH and no thyroid antibodies and during follow up developed TPOAb (cases) or remained without thyroid antibodies (controls). Controls in both studies were matched for age, BMI, smoking status, estrogen use, month of blood sampling and in study B for the duration of follow up.

Results: Study A: The 78 cases had a higher serum 25(OH)D concentration than the 78 controls (21.0±7.9 ng/ml vs. 18.0±6.4 ng/ml, P=0.01). The prevalence of 25(OH)D deficiency (<20 ng/ml) was lower in cases than in controls (48.7% vs. 64.1% respectively, P=0.05); the same was true for the prevalent rates of 25(OH)D deficiency and insufficiency (<30 ng/ml) (83.3% vs. 94.9%, P=0.02).

Study B: The 25(OH)D levels in ng/ml were 22.6±10.3 vs. 23.4±9.1 at baseline and 21.6±9.2 vs. 21.2±9.3 at follow-up (67 cases vs. 67 controls, NS). The frequency of 25(OH)D deficiency (<20 ng/ml) at baseline was comparable in cases and in controls (49.2% vs. 34.3% respectively, p=0.05); the same was true for the prevalent rates of 25(OH)D deficiency and insufficiency (<30 ng/ml) (79.1% vs. 86.5%, P=0.25). Similar figures were obtained at the time of seroconversion.

Conclusions: Early stages of thyroid autoimmunity (in study A genetic susceptibility and in study B development of TPOAb) were not related with low vitamin D levels.

Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.

Funding: This research did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector