When someone starts loading up on anabolic steroids at a very young age and builds their physique only on Anabolic steroids then what happens often is their natural hormones that would preserve their muscle mass starts to decrease over time. Generally bodybuilders like this rarely cycle and barrage their systems with various hormones which causes their natural hormone production to become weaker and weaker. Once they cut the flow of juice off then their bodies have nothing left to build the muscle with since their natural production is severely impaired.
In such circumstances it is very easy to lose massive amounts of muscle mass in very short times, especially if you stop lifting weights all together or get sick. It is possible to lose 100 pounds of muscle mass in less than a year this way. Based on the pictures it looks like Marko lost about 80 pounds in less than a year.
Usually a persons testicles will stop outputting testosterone within a matter of days to weeks of starting steroids.
A steroid user who is unsuccessful in recovering his natural testosterone to normal levels after concluding a cycle (PCT) usually will administer replacement levels of testosteone themselves or legally with the help of a doctor, due to the fact that they will feel like shit with low testosterone.
I doubt this guy would have the drive, aggression or energy to fight in MMA/boxing competitions if he had low levels of testosterone.
If he did so happen to recover his natural testosterone to normal levels after ending his bb career, there is no way that this natural amount of testosterone would support his steroid induced muscle mass.
