The more experienced can jump in here but post cycle therapy (pct) helps with the bodys recovery. After using steroids most of them shut down your natural test because you pump so much of it into your body. besides that estrogen levels, FSH, LH etc are all out of balance and post cycle therapy (pct) will help your body recover and start it's natural production of test which will inturn help you keep the gains you have made during cycle.
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