Testosterone is a steroid sex hormone found in both men and women. In men, testosterone is produced primarily by the Leydig (interstitial) cells of the testes when stimulated by luteinizing hormone (LH). It functions to stimulate spermatogenesis, promote physical and functional maturation of spermatozoa, maintain accessory organs of the male reproductive tract, support development of secondary sexual characteristics, stimulate growth and metabolism throughout the body and influence brain development by stimulating sexual behaviors and sexual drive. In women, testosterone is produced by the ovaries (25%), adrenals (25%) and via peripheral conversion from androstenedione (50%). Testerone in women functions to maintain libido and general wellbeing. Testosterone exerts a negative feedback mechanism on pituitary release of LH and follicle-stimulating hormone (FSH). Testosterone may be further converted to dihydrotestosterone or estradiol depending on the tissue. The effects of testosterone in humans and other vertebrates occur by way of two main mechanisms: by activation of the androgen receptor (directly or as DHT), and by conversion to estradiol and activation of certain estrogen receptors. Free testosterone (T) is transported into the cytoplasm of target tissue cells, where it can bind to the androgen receptor, or can be reduced to 5α-dihydrotestosterone (DHT) by the cytoplasmic enzyme 5α-reductase. DHT binds to the same androgen receptor even more strongly than T, so that its androgenic potency is about 2.5 times that of T. The T-receptor or DHT-receptor complex undergoes a structural change that allows it to move into the cell nucleus and bind directly to specific nucleotide sequences of the chromosomal DNA. The areas of binding are called hormone response elements (HREs), and influence transcriptional activity of certain genes, producing the androgen effects. Testosterone is used as hormone replacement or substitution of diminished or absent endogenous testosterone. Use in males: For management of congenital or acquired hypogonadism, hypogonadism associated with HIV infection, and male climacteric (andopause). Use in females: For palliative treatment of androgen-responsive, advanced, inoperable, metastatis (skeletal) carcinoma of the breast in women who are 1-5 years postmenopausal; testosterone esters may be used in combination with estrogens in the management of moderate to severe vasomotor symptoms associated with menopause in women who do not respond to adequately to estrogen therapy alone.

Etiocholanone is an androstane neurosteroid. Etiocholanone potentiates GABA-A receptor currents and exerts anticolvunsant properties in rodents. Etiocholanolone demostrates pyrogenic properties.

Androsterone sulfate is endogenous, naturally occurring steroid and the the most abundant 5 alpha-reduced androgen metabolite in serum. This steroid is formed from the reaction of sulfation of androsterone and can be desulfated back by the action of steroid sulfatase. It was also found significant and sodium-dependent organic anion transporter SOAT (SLC10A6)-mediated transport of Androsterone sulfate. There existed assumption that may be this steroid could be a marker of systemic 5 alpha-reductase activity, but that was not confirmed and thus androsterone sulfate cannot take into consideration as a marker of either adrenal androgen production or of hirsutism.

STANOLONE, also known as dihydrotestosterone, is a potent androgenic metabolite of testosterone and anabolic agent for systemic use. It may be used as a replacement of male sex steroids in men who have androgen deficiency, for example as a result of the loss of both testes, and also the treatment of certain rare forms of aplastic anemia which are or may be responsive to anabolic androgens.

The compound believed to be principally responsible for the unpleasant odor sometimes produced during cooking of pork or bacon from boars has been isolated and identified as 5a-androst-16-en-3-one. It is the first mammalian pheromone to be identified. Androstenone is the active ingredient in a commercial products which were developed for farmers and breeders who need help determining the best fertilization time for sows and gilts. In humans, androstenone also has been suggested to be a pheromone. Excessive exposures may affect human health, as follows: Upper respiratory tract: Irritation, Dizziness, Drowsiness, Headache, Nausea; Skin: Redness.