Vitamin D deficiency may be a risk factor for ophthalmopathy in patients with Graves' hyperthyroidism but not Hashimoto's thyroiditis

Aims: Apart from its key role in bone metabolism vitamin D plays a role in immune function, cancer prevention and autoimmunity induction. Vitamin D insufficiency (25-50 nmol/L) and deficiency (serum level <25 nmol/L) are very common in the West Sydney and Blue Mountains areas of Australia. Vitamin D deficiency may also play a role in the development of ophthalmopathy in patients with thyroid autoimmunity. Methods: We have studied a possible relationship between serum vitamin D level and ophthalmopathy in patients with Graves' disease and Hashimoto's thyroiditis. We studied 37 patients with Graves' disease and 69 with Hashimoto's thyroiditis at their first clinical visit, before any vitamin D replacement. Results: Overall, 70% of patients with Graves' disease, 86% of those with Hashimoto's thyroiditis and 88% of patients with Multi nodular goiter control group were vitamin D deficient or insufficient. Sixty-one % of Graves' patients who were vitamin D deficient and 75% of those who were vitamin D insufficient had ophthalmopathy, defined as a NOSPECS class of two or more, compared to only 27% of patients who were vitamin D replete, this difference was significant by odds ratio [5.03 (confidence interval 1.06 – 23.8) P=0.03] and showed a trend to significance by X² test (P = 0.08). Thirty nine % of Graves' patients who were vitamin D deficient and 25% of those who were vitamin D insufficient had no ophthalmopathy, compared to 73% of patients who were vitamin D replete. Eleven % of patients with Hashimoto's thyroiditis who were vitamin D deficient and 22% of those who were vitamin D insufficient had ophthalmopathy, which was generally mild and often manifest as isolated upper eyelid retraction, compared to 20% of patients who were vitamin D replete, which was not significant. There was no close correlation between vitamin D status and either the activity or severity of the ophthalmopathy, for either Graves' disease or Hashimoto's thyroiditis. Conclusions: Vitamin D deficiency is significantly associated with ophthalmopathy in patients with Graves' hyperthyroidism but not Hashimoto's thyroiditis. The finding that a normal serum vitamin D level was associated with a decreased prevalence of ophthalmopathy in patients with Graves' hyperthyroidism, but not Hashimoto's thyroiditis, suggests that the pathogenesis of the eye changes in the two disorders may be different. It appears that Graves' patients with ophthalmopathy have a greater propensity to vitamin D deficiency as compared to Graves' patients without ophthalmopathy. While the significance of the findings needs to be addressed in a prospective study it seems that vitamin D deficiency is another risk factor for ophthalmopathy in patients with Graves' hyperthyroidism.