Listen, if Deca (Nandrolone Decanoate) didn't have any side-effects, I'd tell you to take it for the rest of your life, and here's why. Deca is awesome because it does so many things to make you look good. It increases nitrogen retention, protein synthesis, red blood cell production, IGF (insulin growth factor) and even acts as a nutrient partitioning agent! And man, let me tell you, when you're on Deca and a good diet… you'll look like a "Greek God!"
However, because Deca makes you look so freakin' good, it's very dangerous because you'll never want to go-off of it, and "here-in" lies the problem. And that problem is, Deca is so "cosmetically awesome," it's common for guys to take it for up to two years. In fact, I know a former bodybuilder (and convicted steroid trafficker) who stayed on Deca for 8 years without going off! Yes, 8 years! But, let me tell you something else…his immune system is shot-to-hell.
A much better option is to take a non-hormonal anabolic agent called Mesobolin. Mesobolin is an awesome "nitrogen retainer" because both of its anabolic agents were used as steroids in Europe and are listed in the Pharmacopeia, which is the equivalent to the Physician Desk Reference here in the U.S!
If you haven't heard of ecdysterones, then you don't know what you're missing, because this naturally occurring compound is known to function in much the same way as steroids, but naturally, meaning no steroidal side-effects. Many users report enormous muscular gains, sometimes even beyond what they experienced with synthetic compounds like Deca! And that is really saying something big!