Testosterone was a substance produced by the body.
While watching a tense exchange between the Ninth Doctor and Henry van Statten, Rose Tyler quipped she could "smell the testosterone". (TV: Dalek)
The Mire fed on adrenalin and testosterone. (TV: The Girl Who Died)
Water Hags required testosterone to complete their birth cycle. (PROSE: Something in the Water)
Though Sontarans possessed both male and female chromosomes, they produced such high amounts of testosterones in their youth that they were all born male. As they aged, the levels dipped enough for the female chromosomes to dominate. (AUDIO: Salvation Nine)