In a study presented to the Am Academy of Dermatology, the researchers associated with McNeil, makers of the 1% OTC version of Nizoral Shampoo found that it had, as it has been shown for the 2% precription version, beneficial effects on Androgenetic Alopecia (MPB).
In short they found that 1% Nizoral Shampoo reduced sebum emission, and increased hair shaft diameter (which decreases in MPB) after being used 2-3 times a week for a period of 6 months. They also found a percentage increase in the overall number of anagen hairs, which typically decreased overtime in MPB. By comparison they found Zinc Pyrithione Shampoo (Head and Shoulders) did not decrease sebum emission or increase hair shaft diameter, but did increase the overall number of anagen hairs as well.
The decrease in sebum emission caused by 1% Nizoral Shampoo, seems to confirm its antiandrogenic action, which is though by most to be only one of the reasons it helps hair loss.