MASTERJOHN: none of these has as much evidence for being a very common cause of hair loss as iron deficiency. In other words, iron deficiency is a primary driver of hair loss

...but none of these has as much evidence for being a very common cause of hair loss as iron deficiency.

— Chris Masterjohn (@ChrisMasterjohn) June 2, 2024

In 100 women with androgenetic alopecia, the first 50 were tested and 36 of them had ferritin concentrations below that of the lowest control (40 mg/mL).  --Chris Masterjohn.

Boosting iron is beneficial but incomplete.  

But if suboptimal iron status is a major but incomplete part of the suboptimal energy metabolism in your hair follicle, getting your iron levels up is likely to provide very large but incomplete benefits.