Serenoa repens (Saw palmetto) present in southeastern parts of United States, it is a small palm tree having large leaves and deep red black berries. Saw palmetto extract inhibits the binding of dihydrotestosterone (DHT) to the receptors and blocks there activity. It has been seen in the past that there is a relation between the hair loss pattern and the level of 5 alpha-reductase. This 5 alpha-reductase converts the hormone testosterone into DHT. It has also been noted that in cases of hair loss there is high levels of DHT at the Scalp. DHT can contributes to the shortening of the growth phase and thinning of the hair (1).
References:
1. Chizick, S. and Delorscio, R. 1999. Natural preparation for treatment of male pattern hair loss. US Patent 5,972,345. Assigned to Proguard. Issued October 26, 1999
