Androstadienone, also known as androsta-4,16,-dien-3-one, is an endogenoussteroid that has been described as having potent pheromone-like activities in humans. The compound is synthesized from androstadienol by 3β-hydroxysteroid dehydrogenase, and can be converted into androstenone (a more potent and odorous pheromone) by 5α-reductase, which can subsequently be converted into 3α-androstenol or 3β-androstenol (also more potent and odorous pheromones) by 3-ketosteroid reductase. Androstadienone is related to the androgensex hormones; however, androstadienone does not exhibit any androgenic or anabolic effects. Though it has been reported to significantly affect the mood of heterosexual women and homosexual men, it does not alter behavior overtly, although it may have more subtle effects on attention. Androstadienone is commonly sold in male fragrances; it is purported to increase sexual attraction, but there is no convincing evidence of its effectiveness. Androstadienone, in picogram quantities, has been shown to have "significant reduction of nervousness, tension and other negative feeling states" in female subjects .
In 2014, a researcher found that the brains of adolescents with gender dysphoria react to the sex hormone androstadienone in a measurable way similar to the brains of people of the gender with which the person identifies.