11β-Hydroxysteroid dehydrogenase type 1, also known as cortisone reductase, is an NADPH-dependent enzyme highly expressed in key metabolic tissues including liver, adipose tissue, and the central nervous system. In these tissues, HSD11B1 reduces cortisone to the active hormone cortisol that activates glucocorticoid receptors. It belongs to the family of short-chain dehydrogenases. It is encoded by the HSD11B1 gene.
3β-Hydroxysteroid dehydrogenase/Δ5-4 isomerase (3β-HSD) is an enzyme that catalyzes the biosynthesis of the steroid progesterone from pregnenolone, 17α-hydroxyprogesterone from 17α-hydroxypregnenolone, and androstenedione from dehydroepiandrosterone (DHEA) in the adrenal gland. It is the only enzyme in the adrenal pathway of corticosteroid synthesis that is not a member of the cytochrome P450 family. It is also present in other steroid-producing tissues, including the ovary, testis and placenta. In humans, there are two 3β-HSD isozymes encoded by the HSD3B1 and HSD3B2 genes.
17β-Hydroxysteroid dehydrogenases, also 17-ketosteroid reductases (17-KSR), are a group of alcohol oxidoreductases which catalyze the reduction of 17-ketosteroids and the dehydrogenation of 17β-hydroxysteroids in steroidogenesis and steroid metabolism. This includes interconversion of DHEA and androstenediol, androstenedione and testosterone, and estrone and estradiol.
The human gene SRD5A2 encodes the 3-oxo-5α-steroid 4-dehydrogenase 2 enzyme, also known as 5α-reductase type 2 (5αR2), one of three isozymes of 5α-reductase.
17β-Hydroxysteroid dehydrogenase 1 (17β-HSD1) is an enzyme that in humans is encoded by the HSD17B1 gene. This enzyme oxidizes or reduces the C17 hydroxy/keto group of androgens and estrogens and hence is able to regulate the potency of these sex steroids
HSD3B2 is a human gene that encodes for 3beta-hydroxysteroid dehydrogenase/delta(5)-delta(4)isomerase type II or hydroxy-delta-5-steroid dehydrogenase, 3 beta- and steroid delta-isomerase 2. It is expressed principally in steroidogenic tissues and is essential for steroid hormone production. A notable exception is the placenta, where HSD3B1 is critical for progesterone production by this tissue.
Aldo-keto reductase family 1 member C3 (AKR1C3), also known as 17β-hydroxysteroid dehydrogenase type 5 is a key steroidogenic enzyme that in humans is encoded by the AKR1C3 gene.
Aldo-keto reductase family 1 member C1 also known as 20α-hydroxysteroid dehydrogenase, 3α-hydroxysteroid dehydrogenase, and dihydrodiol dehydrogenase 1/2 is an enzyme that in humans is encoded by the AKR1C1 gene.
D-bifunctional protein (DBP), also known as peroxisomal multifunctional enzyme type 2 (MFP-2), as well as 17β-hydroxysteroid dehydrogenase type IV is a protein that in humans is encoded by the HSD17B4 gene. It's an alcohol oxidoreductase, specifically 17β-Hydroxysteroid dehydrogenase. It is involved in fatty acid β-oxidation and steroid metabolism.
17β-Hydroxysteroid dehydrogenase 2 (17β-HSD2) is an enzyme of the 17β-hydroxysteroid dehydrogenase (17β-HSD) family that in humans is encoded by the HSD17B2 gene.
3α-Hydroxysteroid dehydrogenase is an enzyme that in humans is encoded by the AKR1C4 gene. It is known to be necessary for the synthesis of the endogenous neurosteroids allopregnanolone, THDOC, and 3α-androstanediol. It is also known to catalyze the reversible conversion of 3α-androstanediol (5α-androstane-3α,17β-diol) to dihydrotestosterone and vice versa.
17β-Hydroxysteroid dehydrogenase 3 (17β-HSD3) is an enzyme that in humans is encoded by the HSD17B3 gene and is involved in androgen steroidogenesis.
Estradiol 17-beta-dehydrogenase 12 is an enzyme that in humans is encoded by the HSD17B12 gene.
Hydroxysteroid 17-beta dehydrogenase 6 is an enzyme that in humans is encoded by the HSD17B6 gene.
Epiandrosterone, or isoandrosterone, also known as 3β-androsterone, 3β-hydroxy-5α-androstan-17-one, or 5α-androstan-3β-ol-17-one, is a steroid hormone with weak androgenic activity. It is a metabolite of testosterone and dihydrotestosterone (DHT). It was first isolated in 1931, by Adolf Friedrich Johann Butenandt and Kurt Tscherning. They distilled over 17,000 litres of male urine, from which they got 50 milligrams of crystalline androsterone, which was sufficient to find that the chemical formula was very similar to estrone.
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).
11α-Hydroxyprogesterone (11α-OHP), or 11α-hydroxypregn-4-ene-3,20-dione is an endogenous steroid and metabolite of progesterone. It is a weak antiandrogen, and is devoid of androgenic, estrogenic, and progestogenic activity.
Steroidogenic enzymes are enzymes that are involved in steroidogenesis and steroid biosynthesis. They are responsible for the biosynthesis of the steroid hormones, including sex steroids and corticosteroids, as well as neurosteroids, from cholesterol. Steroidogenic enzymes are most highly expressed in classical steroidogenic tissues, such as the testis, ovary, and adrenal cortex, but are also present in other tissues in the body.
The androgen backdoor pathway is a collective name for all metabolic pathways where clinically relevant androgens are synthesized from 21-carbon steroids (pregnanes) by their 5α-reduction, bypassing testosterone and/or androstenedione.
