I think the answer is due to the fact that in order for oral anabolics to get into the blood - they must pass thru the liver. Scientitst added a particular molecule (17-AA) to the drug in order to make sure the drug is able to make it through this "first pass" of the liver without being rendered ineffective. The problem is this 17-AA molecule creates a very heavy burden on the liver. The liver must keep grinding through this 17-AA molecule in order to eventually clear the drug.
On the other hand, acetomeniphine (Tylenol) does not require this molecule. However, the drug itsef has proven to be mildy hepatoxic.
Can't really compare the two because they are hepatoxic for different reasons - bottom line 17-AA orals are highly hepatoxic, where as Tylenol is very mildly hepatoxic.