According to the PDR 2006 testosterone is only effective in the cells when it is converted to Dihydrotestosterone (DHT). This requires the enzyme 5-Alpha reductase. However, many Test users supplement their cycles with Propecia (a 5-Alpha reductase inhibitor) to reduce hair loss or preven benign prostatic hyperplasia (enlarged prostrate). Has anyone found that their gains are not as effective with this combination therapy?????