Testosterone boosters What is testosterone responsible for in the male body? What happens when there is a testosterone deficiency? Why are testosterone boosters becoming more and more popular? What are the characteristics of such products? You will find answers to all these questions in the article below. What is testosterone responsible for? In the case of men it is the most important sex hormone. Interestingly, over 90% of testosterone is produced by the parenchymal cells of the testes (the rest is produced in the adrenal glands).