Sexual Dimorphism of Growth Plate Prehypertrophic and Hypertrophic Chondrocytes in Response to Testosterone Requires Metabolism to Dihydrotestosterone by Steroid 5-Alpha Reductase Type 1

The study investigated the sex-specific responses of rat costochondral growth plate chondrocytes to testosterone, revealing that only male cells responded to the hormone. This response required the metabolism of testosterone to dihydrotestosterone (DHT) by steroid 5-alpha reductase type 1. Male growth zone chondrocytes showed increased DNA synthesis and alkaline phosphatase activity when treated with testosterone and DHT, while female cells did not respond, likely due to their ability to convert testosterone to estradiol instead. The study highlighted the necessity of DHT for the male-specific response and the absence of 5-alpha reductase activity in female cells.