Why carry out this study?

Alopecia areata (AA) is a form of non-scarring hair loss characterized by an autoimmune reaction to hair follicles with disordered, shortened hair cycle

Vitamin D deficiency was considered as a risk factor for the development of AA

The relationship between vitamin D deficiency and AA in patients was reported in two previous meta-analyses but not comprehensively evaluated because five subsequent studies were not considered

What was learned from the study?

Deficiency of serum 25(OH)D level, rather than calcium level, was present in patients with AA. Screening for vitamin D deficiency and vitamin D supplementation may be beneficial in treatment of patients with AA