TPO and autoimmune thyroid disease: Among vitamin D-deficient cases, an increased serum 25(OH)D ≥ 50 nmol/L was associated with greater reductions in biochemical signs of hypothyroidism and thyroid autoimmune disease including an increase in FT4 and FT3, and large decrease in serum TSH, anti-TPO, anti-TG, and TG (Supplementary Table 5).