I started a thread awhile back on this
M5AA/hair loss experiences?
In theory since this converts to methyl-DHT (From designer supp website) it should be pretty androgenic. However, feedback from users, while limited, seems to suggest that with proper precautions it may be possible to take without hairloss. (Sledge does give a possible explanation which I quoted in the previos thread.) Run a search on bb.com on hair loss and there is a good thread.
Dont be surprised if someone flat out mocks you for being worried about hair loss and thinking about taking M5aa.