The thyroid-stimulating hormone was statistically higher and the free T4 was statistically lower in the 25(OH)D-deficient group than in normal controls. The 25(OH)D-deficient group had higher odds of both subclinical and clinical hypothyroidism compared to controls. A significant negative correlation between the 25(OH)D and TSH, and a significant positive correlation between the 25(OH)D and the free T4 were detected in this study.