Saw palmetto works by inhibiting 5 alpha reductase, a key enzyme in the breakdown of testosterone into dihydrotestosterone (DHT). DHT is more potent, meaning that it binds more effectively to androgen receptors. By blocking this process, you keep androgen levels low. Typically used in the treatment of prostate hyperplasia, it's thought that reducing androgen levels in women with PCOS can help reduce the severity of the syndrome and even treat some of the symptoms.
Saw palmetto is generally well tolerated, though you should speak with your doctor before starting this supplement. It should not be taken with other blood thinners, like aspirin or lovenox because of the potential for serious interactions. Saw palmetto may also interact with other medications used to treat PCOS, like the birth control pill, finasteride or spironolactone, so make sure to speak with your doctor.
Because of the hormonal action of this supplement, it should not be taken by pregnant or breastfeeding women.
The recommended dosage for men is 320mg daily in two divided doses. Speak with your physician or natural practitioner about what s/he suggests.