For a long time it was claimed that all AAS are suppressive and that it is only a matter of time before they completely shut down natural testosterone production. THIS IS NOT TRUE.
In fact, most oral AAS are only mildly suppressive at normal doses and practically never completely stop natural testosterone production. Of course, if they are taken in very high doses, then stronger suppression will occur.
Among the most suppressive oral AAS are Methandienone and Methyltestosterone, both of which are practically equal in this respect. All other oral AAS cause only mild to moderate suppression.
Example: 15 mg of Methandienone is as suppressive as 150 mg of Oxymetholone.
Non-aromatizing oral AAS are less suppressive than those that aromatize. Another example: 20 mg of Turinabol daily suppresses LH and FSH by only 10–20% on average, whereas 15 mg of Methandienone daily suppresses LH and FSH by about 50%.
In any case, no oral AAS can suppress natural testosterone production as much as injectable AAS. Overall, injectable synthetic testosterone is among the most suppressive AAS in general, although there is one AAS — Trestolone — that is even more suppressive, which is why it was studied for male contraception (unsuccessfully).
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