Lower levels of TSH in vitamin D sufficient Graves patients and higher rates of vitamin D deficiency in graves patients: a case-control study
Abstract Vitamin D deficiency is associated with an increased incidence of autoimmune thyroid diseases. Its association with Hashimoto has previously been discussed in several studies, but its role in Graves' disease is yet to be elucidated; the aim of this study was to evaluate the effect of vitamin D on hyperthyroid patients regardless of the cause (autoimmune, non-autoimmune and control) . A total of 187 patients were divided into three groups: 74 patients with autoimmune hyperthyroidism (Graves), 43 non-immune patients (Toxic thyroid adenoma and goiter multi-nodular) and 70 healthy patients as the control group. The primary outcome was the frequency of vitamin D deficient patients and the level of vitamin D in each group. The secondary outcomes were measured as the values of anti-thyroid antibody and anti-thyroglobulin antibodies, TSH, T3, and T4. Based on the results, higher levels of TSH were observed in Graves patients who were vitamin D sufficient in comparison to Graves subjects with moderate vitamin D deficiency (P=0.022). Also, vitamin D sufficient control subjects had higher TSH levels than subjects with severe (p<0.0001) and moderate (P<0.0001) vitamin D deficiency. Vitamin D deficiency was more frequent in Graves patients, however the difference was not significant (P-value>0.05). Vitamin D deficiency as an effective factor in thyroid autoimmune diseases is more frequent in autoimmune hyperthyroid disease patients. Moreover, vitamin D sufficient Graves' participants had higher TSH levels compared with vitamin D deficient ones, probably protecting them from developing osteoporosis. Low TSH levels in hyperthyroid patients are one of the osteoporosis risk factors.