Saw Palmetto extract is derived from the fruit of a palm tree.
It is commonly claimed to be a treatment for pattern hair loss (androgenic alopecia). Some say it works by preventing the conversion of testosterone to DHT in a similar way to the prescription medication Finasteride.
Here is an example claim from the popular Dr. Mercola web-site:
Saw palmetto inhibits an enzyme called 5-alpha reductase, which converts testosterone to a powerful androgen hormone known as dihydrotestosterone, or DHT
It significantly triggered follicle growth and decreased inflammatory response even better than finasteride (Propecia)
Source: Saw Palmetto for Hair Loss?
The page cites a number of studies.
Is Saw Palmetto extract an effective treatment for pattern hair loss?