noun, plural: androstenediones
A steroid hormone, with a chemical formula of C19H26O2, and a common precursor of androgen and estrogen
Androgen is one of the major classes of sex steroids (or sex hormones) of vertebrates, including humans. Androgens include androstenediol (A5), androstenedione (A4), dehydroepiandrosterone (DHEA), dihydrotestosterone (DHT), androsterone, and testosterone. Androstenedione (A4) is an unsaturated, weak endogenous androgen that occurs as three isomers. It is structurally related to A5. A4 is naturally produced and secreted by testes, ovaries, and adrenal cortex. It is a precursor to male and female sex hormones (i.e. testosterone and estrone) from DHEA. It has been found to have some estrogenic activity. Nevertheless, compared with other metabolites, such as A5, the A4 has very low affinity for estrogen receptors (ER), i.e. less than 0.01% of affinity for both ERα and ERβ.1
During adrenarche (early sexual maturation stage) of primates (including humans), A4 and DHEA levels rise. The rise of A4 and DHEA at adrenarche is presumed to have a role in aggression and competition in boys, and in the development of other social skills or behavior.
Gonadal androstenediones are produced as regulated by adrenocorticotrophic hormone (ACTH) . Adrenal androstenediones are produced under the control of gonadotropins. The androstenediones may be converted to either testosterone with the help of the enzyme 17β-hydroxysteroid dehydrogenase or to estrone with the help of the enzyme aromatase.
A4 may also be synthesized synthetically. It is one of the anabolic steroids. It is administered orally. Nevertheless, the use of A5 as a bodybuilding supplement is banned by sporting organizations.
1 Kuiper, G. G., Carlsson, B., Grandien, K., Enmark, E., Häggblad, J., Nilsson, S., & Gustafsson, J. A. (March 1997). “Comparison of the ligand binding specificity and transcript tissue distribution of estrogen receptors alpha and beta”. Endocrinology. 138 (3): 863–70. doi:10.1210/endo.138.3.4979