In order to use post cycle therapy (PCT) properly, we must first understand how anabolic steroids work. The fundamental misconception is that muscles grow when you take steroids. No, they don't grow. Muscle cells only increase their volume because they are filled with nutrients. Muscles can only grow by dividing a muscle cell, such is the effect of growth hormone or IGF. So if you don't time PCT correctly, you will lose all your muscles after stopping on steroids. Properly selected substances in post cycle therapy will ensure that your natural testosterone returns to normal levels as quickly as possible, thus maintaining the maximum amount of muscle after the cycle. The classic known substance that will help us restore our own testosterone production is the hormone HCG or a product with the active substance clomiphene. Furthermore, Tamoxifen is sometimes included in PCT because it prevents gynecomastia - the growth of the finger gland in men.