Dietary supplements are commonly used among athletes. The Australian Institute of Sport (AIS) groups supplements into 4 categories, being group D considered by the World Anti-Doping Agency (WADA) as prohibited supplements. The online availability of four doping substances: oxandrolone, dehydroepiandrosterone (DHEA), androstenedione and Tribulus terrestris, purchased from Spain, Puerto Rico, Canada, USA, Ukraine and Russia was evaluated. The characteristics of the websites, the countries the webs sold to, the pharmaceutical forms offered and the recommendations for its use were analyzed by using a computer tool designed ad hoc. There were significant differences between countries in the number of webpages that sold the products (Chi-square test, p<0.05). Oxandrolone was available for purchase mainly in Spain (27.12%) and Ukraine (26.58%), coming from websites dedicated to sports (77.26%). For DHEA, most of the pages were located in Canada (23.34%) and Russia (21.44%). Tribulus terrestris was the compound with the highest number of web pages. In the case of androstenedione, none of the pages for its sale requested prescription. Products such as androstenedione or DHEA are claimed to enhance sports performance or for sports use without providing details. The results showed that a limited number of Internet sites request prescriptions. Most of the doping substances are purchased from the country where they are requested. Athletes should be encouraged to consult health professionals about which supplements are suitable for their type of training and sports objectives.

Testosterone holds significant medical and economic importance, with the global market for testosterone replacement therapies valued at approximately $1.9 billion in 2023. This hormone is essential for the development and maintenance of male sexual characteristics as well as bone and muscle health. It plays a key role in conditions such as hypogonadism, muscle disorders, and andropause. However, the industrial production of testosterone often involves complex chemical processes that result in low yields, high costs, and environmental damage. Microbial biotransformation of steroids presents an eco-friendly alternative to traditional chemical synthesis. A knockout strain of Aspergillus nidulans deficient in steroid 11-α-hydroxylase activity was developed, rendering it incapable of hydroxylating androstenedione, progesterone, and testosterone. In this strain, two newly identified CYP450 enzymes—CYP68L1 from A. nidulans and CYP68L8 from Aspergillus ochraceus—were expressed to confirm their roles as steroid 11-α-hydroxylases. These enzymes successfully hydroxylated steroids such as androstenedione, progesterone, and testosterone. The availability of these 11-α-hydroxylases represents significant progress toward achieving efficient single-step steroid fermentation. Furthermore, the A. nidulans knockout strain is proposed as an effective model for studying the conversion of androstenedione to testosterone owing to its inability to hydroxylate the testosterone produced during bioconversion.