Purpose: To investigate serum 25-hydroxyvitamin D 25(OH)D status and assess the predictability of outcome in patients with Graves' disease (GD) who received a patient-specific calculated dose of radioiodine therapy (RIT).
Methods: 128 patients with GD who received RIT from July 2010 to September 2010 were included. Pre-therapy serum levels of 25(OH)D, calcium, phosphorus, parathyroid hormone, free triiodothyronine, free thyroxine, thyroid stimulating hormone and creatinine were measured. 60 age- and BMI-matched healthy subjects were chosen as the normal control group.
Results: Post-therapy follow-up results revealed that therapy failed in 25.00 % of the patients. Serum 25(OH)D levels were found to be significantly lower in patients who failed in therapy. The prevalence of vitamin D deficiency in GD patients was significantly higher compared with control subjects (56.25 vs. 10.00 %, P < 0.001), and therapy failed in 27 (37.50 %) of these patients whose serum 25(OH)D levels < 20 ng/ml. Out of the 56 patients (43.75 %) in whom serum 25(OH)D levels ≥20 ng/ml, therapy was unsuccessful in only 5 (8.93 %). Cox regression analysis suggested that serum 25(OH)D levels <20 ng/ml might be an independent risk factor for predicting failure of RIT in GD patients (relative risk = 8.83, 95 % confidence interval = 3.34-23.38, P < 0.001).
Conclusions: Serum 25(OH)D levels were lower in patients who failed than in those who succeeded in RIT of GD. Therefore, serum 25(OH)D < 20 ng/ml might be an independent risk factor for predicting failure of RIT in GD patients.
Keywords: 25-Hydroxyvitamin D; Graves’ disease; Hyperthyroidism; Prognosis; Radioiodine therapy.