Androstenol, also known as 5α-androst-16-en-3α-ol (shortened to 3α,5α-androstenol or 3α-androstenol), is a 16-androstene class steroidal

pheromone A pheromone () is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting like hormones outside the body of the secreting individual, to affect the behavio ...

and neurosteroid in humans and other mammals, notably pigs. It possesses a characteristic

musk Musk ( Persian: مشک, ''Mushk'') is a class of aromatic substances commonly used as base notes in perfumery. They include glandular secretions from animals such as the musk deer, numerous plants emitting similar fragrances, and artificial sub ...

-like odor. Androstenol, or a derivative, is found in black truffles. This was offered as an explanation for how pigs locate them deep in the ground: Androstenol is produced in the saliva of male pigs. However, experiments in France using pigs to scent truffles, truffle scent extract, and purified androstenol showed that pigs responded to the first two (actually trying to eat dirt containing the truffle extract), but ignored the androstenol. A

positional isomer In chemistry, a structural isomer (or constitutional isomer in the IUPAC nomenclature) of a compound is another compound whose molecule has the same number of atoms of each element, but with logically distinct bonds between them. The term meta ...

of androstenol, 3β-androstenol (5α-androst-16-en-3β-ol), is also endogenous to humans (as well as to pigs), behaving as a pheromone and contributing to axillary odor.

Biosynthesis

In humans and boars, androstenol is

biosynthesized Biosynthesis is a multi-step, enzyme- catalyzed process where substrates are converted into more complex products in living organisms. In biosynthesis, simple compounds are modified, converted into other compounds, or joined to form macromolecules ...

in the

testes A testicle or testis (plural testes) is the male reproductive gland or gonad in all bilaterians, including humans. It is homologous to the female ovary. The functions of the testes are to produce both sperm and androgens, primarily testoste ...

Pregnenolone Pregnenolone (P5), or pregn-5-en-3β-ol-20-one, is an endogenous steroid and precursor/ metabolic intermediate in the biosynthesis of most of the steroid hormones, including the progestogens, androgens, estrogens, glucocorticoids, and mineraloc ...

is metabolized into

androstadienol Androstadienol, or androsta-5,16-dien-3β-ol, is a 16-androstene class endogenous steroid, pheromone, and chemical intermediate to several other pheromones that is found in the sweat of both men and women. Androstadienol and androstadienone ...

by the 16-ene-synthetase activity of

CYP17A1 Cytochrome P450 17A1 (steroid 17α-monooxygenase, 17α-hydroxylase, 17-alpha-hydroxylase, 17,20-lyase, 17,20-desmolase) is an enzyme of the hydroxylase type that in humans is encoded by the ''CYP17A1'' gene on chromosome 10. It is ubiquitously exp ...

. Androstadienol is then sequentially converted into androstenol by 3β-hydroxysteroid dehydrogenase (

androstadienone Androstadienone, or androsta-4,16-dien-3-one, is a 16-androstene class endogenous steroid that has been described as having potent pheromone-like activities in humans. The compound is synthesized from androstadienol by 3β-hydroxysteroid dehydr ...

), 5α-reductase (androstadienone to androstenone), and 3α-hydroxysteroid dehydrogenase (androstenone to androstenol), in a manner analogous to the biosynthesis of 3α-androstanediol from

dehydroepiandrosterone Dehydroepiandrosterone (DHEA), also known as androstenolone, is an endogenous steroid hormone precursor. It is one of the most abundant circulating steroids in humans. DHEA is produced in the adrenal glands, the gonads, and the brain. It fun ...

(DHEA). Androstenol may also be synthesized in the

adrenal gland The adrenal glands (also known as suprarenal glands) are endocrine glands that produce a variety of hormones including adrenaline and the steroids aldosterone and cortisol. They are found above the kidneys. Each gland has an outer cortex whic ...

s and the

ovaries The ovary is an organ in the female reproductive system that produces an ovum. When released, this travels down the fallopian tube into the uterus, where it may become fertilized by a sperm. There is an ovary () found on each side of the body. T ...

in humans. In addition, androstenol may be synthesized in the human

nasal mucosa The nasal mucosa lines the nasal cavity. It is part of the respiratory mucosa, the mucous membrane lining the respiratory tract. The nasal mucosa is intimately adherent to the periosteum or perichondrium of the nasal conchae. It is continuous w ...

from androstenone, and likely also from androstadienol and androstadienone in this area.

Distribution

Considerable amounts of androstenol are present in human urine, and it is also present in the blood plasma and saliva of humans and pigs as well as in the

axilla The axilla (also, armpit, underarm or oxter) is the area on the human body directly under the shoulder joint. It includes the axillary space, an anatomical space within the shoulder girdle between the arm and the thoracic cage, bounded superior ...

sweat Perspiration, also known as sweating, is the production of fluids secreted by the sweat glands in the skin of mammals. Two types of sweat glands can be found in humans: eccrine glands and apocrine glands. The eccrine sweat glands are distrib ...

of humans. Due to its ability to cross the blood-brain-barrier, androstenol is likely present in the

central nervous system The central nervous system (CNS) is the part of the nervous system consisting primarily of the brain and spinal cord. The CNS is so named because the brain integrates the received information and coordinates and influences the activity of all p ...

as well.

Biological activity

Androstenol, similarly to the related endogenous steroids 3α-androstanediol and

androsterone Androsterone, or 3α-hydroxy-5α-androstan-17-one, is an endogenous steroid hormone, neurosteroid, and putative pheromone. It is a weak androgen with a potency that is approximately 1/7 that of testosterone. Androsterone is a metabolite of test ...

, has been found to act as a potent

positive allosteric modulator In pharmacology and biochemistry, allosteric modulators are a group of substances that bind to a receptor to change that receptor's response to stimulus. Some of them, like benzodiazepines, are drugs. The site that an allosteric modulator binds to ...

of the GABA_A. It has been proposed that this action may mediate the pheromone effects of androstenol. Moreover, as androstadienol, androstadienone, and androstenone are all converted into androstenol, it could mediate their pheromone effects as well. In animals, androstenol has been found to produce

anxiolytic An anxiolytic (; also antipanic or antianxiety agent) is a medication or other intervention that reduces anxiety. This effect is in contrast to anxiogenic agents which increase anxiety. Anxiolytic medications are used for the treatment of anxiet ...

-like, antidepressant-like, and anticonvulsant effects. Androstenol has also been found to modify the behavioral and social responses of humans. In addition, androstenol has been found to decrease

luteinizing hormone Luteinizing hormone (LH, also known as luteinising hormone, lutropin and sometimes lutrophin) is a hormone produced by gonadotropic cells in the anterior pituitary gland. The production of LH is regulated by gonadotropin-releasing hormone (GnRH) ...

(LH) pulse frequency during the

follicular phase The follicular phase, also known as the preovulatory phase or proliferative phase, is the phase of the estrous cycle (or, in primates for example, the menstrual cycle) during which follicles in the ovary mature from primary follicle to a ful ...

of the human menstrual cycle. In accordance, it has been proposed that androstenol may be involved in the menstrual synchrony of women. In contrast to androstenol (3α-androstenol), its 3β-epimer, 3β-androstenol, does not potentiate the GABA_A receptor, even at high concentrations. This is in accordance with other 3β-hydroxy steroids, including isopregnanolone, epipregnanolone, 3β-dihydroprogesterone, and

3β-androstanediol 3β-Androstanediol, also known as 5α-androstane-3β,17β-diol, and sometimes shortened in the literature to 3β-diol, is an endogenous steroid hormone and a metabolite of androgens like dehydroepiandrosterone (DHEA) and dihydrotestosterone (DHT) ...

, which similarly do not act as such, in contrast to their 3α-hydroxy variants. Androstenol, along with several isomers of androstanol, is an antagonist of the

constitutive androstane receptor The constitutive androstane receptor (CAR) also known as nuclear receptor subfamily 1, group I, member 3 is a protein that in humans is encoded by the ''NR1I3'' gene. CAR is a member of the nuclear receptor superfamily and along with pregnane ...

(CAR). Androstenol has minimal or no

androgen An androgen (from Greek ''andr-'', the stem of the word meaning "man") is any natural or synthetic steroid hormone that regulates the development and maintenance of male characteristics in vertebrates by binding to androgen receptors. This in ...

ic activity.

References

{{Xenobiotic-sensing receptor modulators Androstanes Cyclopentenes GABAA receptor positive allosteric modulators Human pheromones Mammalian pheromones Neurosteroids

Biosynthesis

Distribution

Biological activity

See also

References