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, focusing on the necessity of its metabolism to dihydrotestosterone (DHT) by steroid 5-alpha reductase type 1. It was found that only male chondrocytes responded to testosterone and DHT, despite both male and female cells having testosterone receptors. The response in male cells was dependent on the conversion of testosterone to DHT, as shown by the reduced response when steroid 5α-reductase was inhibited. Male cells expressed mRNAs for steroid 5α-reductase type 1 and exhibited enzyme activity, unlike female cells. The study concluded that the sex-specific response in male growth zone chondrocytes was maturation-state dependent and that female chondrocytes' lack of response might be due to their ability to convert testosterone to estradiol instead.