7α-hydroxytestosterone is an androstanoid that is testosterone substituted by a α-hydroxy group at position 7. It is a polar testosterone metabolite first identified by incubation of testes of adult rats with testosterone. Cytochrome P450 2A1 (CYP2A1) present in rat testis catalyzes the metabolism of testosterone into 7α-hydroxytestosterone. 7α-hydroxytestosterone is also a natural product found in Daphnia magna exposed to the biocide tributyltin. It has been reported to inhibit steroidogenic enzymes in testis including 5α-reductase and 3α-hydroxysteroid dehydrogenase (17β-HSD3). In the developing rat testis and Leydig cells 7 alpha-hydroxytestosterone effected the activity of 11 beta-hydroxysteroid dehydrogenase type 1 (11 beta-HSD1), enzyme that interconverts active corticosterone and inactive 11-dehydrocorticosterone. It competitively suppressed 11 beta-HSD1 oxidase and reductase activities in rat testis microsome preparations and regulated the direction of 11 beta-HSD1 activity in rat Leydig cells. 7-hydroxytestosterone does not influence rat seminal vesicle weight nor does it induce thermogenic enzymes. It was reported that 7a-hydroxytestosterone has no androgenic activity as measured by its lack of effect on maintenance of acid phosphatase in the prostate of castrated rats.