Low iron levels.

A 1968 letter to the editor discussed a study involving 28 women with androgenetic alopecia, aged 20 to post-menopausal, which found that both serum iron levels and serum iron binding capacities were normal. The study suggested that changes in hair follicles were unlikely to be related to iron deficiency. Instead, androgenetic alopecia was considered a normal response of hair follicles to aging and normal hormonal changes.