<prompt> Most of the testosterone secreted by the testes exists in the plasma in the form of?Dihydrotestosterone bound to gonadal steroid-binding hormoneFree dihydrotestosteroneFree testosteroneTestosterone bound to sex-steroid-binding globulin  <response>: The majority of circulating testosterone is bound to plasma protein around 98, rather than existing in free form. Of this, a majority is bound to a specific sex or gonadal steroid-binding protein and a minority is bound to albumin. Dihydrotestosterone is produced from testosterone in the tissues by a specific enzyme, 5-alpha-reductase, rather than circulating in bound or free form. 