11-Ketotestosterone (11-KT) is an oxidized form of testosterone that contains a keto group at the C11 position. It is related to adrenosterone, an androgen found in trace quantities in humans. In fish, 11-ketotestosterone functions as the endogenous androgenic sex hormone.[1][2] In midshipman fish, 11-ketotestosterone is not present in females or Type II Males — Type II Males reach sexual maturation later, are less territorial, and have higher testosterone than Type I Males.
In mammals, 11-ketotestosterone has similar potency to testosterone as an androgen, and has been identified as an important adrenal androgen.[3] However, unlike testosterone, it is very weakly anabolic and mostly prevents muscle breakdown as opposed to promoting muscle growth. It is synthesized from 11β-hydroxyandrostenedione and, to a lesser extent, 11-ketoandrostenedione (adrenosterone).[3] 11-Ketoandrostenedione has notably been sold online as an androgen prohormone, usually under the name 11-oxoandrostenedione (11-OXO).[3]
^Nelson RF (2005). An introduction to behavioral endocrinology. Sunderland, Mass: Sinauer Associates. p. 143. ISBN0-87893-617-3.
^Nagahama Y, Miura T, Kobayashi T (1994). "The Onset of Spermatogenesis in Fish". Germline Development. Ciba Foundation Symposium. Vol. 182. pp. 255–67, discussion 267–70. doi:10.1002/9780470514573.ch14. ISBN9780470514573. PMID7835154.