Do a search. You'll find plenty of threads that explain hairloss and
AAS.
ALL
AAS will cause some form of hairloss if you are destined.
If MPB runs in your family, then
AAS use will most definitely accelerate your hairloss.
You will find that deca is safer on hairloss than other
AAS, but using deca alone may pose other problems.
You can supplement finasteride or dutasteride, both 5-alpha-reductase inhibitors if you use TESTOSTERONE, to help slow the process.
Using either of these along with deca however, will revert deca to as androgenic as many other highly androgenic
AAS.
Just do a search--there was a recent thread that covered most of your questions and offered links to other relevant info.
Happy research.