Genes coding for 17β-HSD include: •
HSD17B1: Referred to as "estrogenic". Major subtype for activation of estrogens from weaker forms (estrone to estradiol and
16α-hydroxyestrone to estriol). Catalyzes the final step in the biosynthesis of estrogens. Highly selective for estrogens; 100-fold higher affinity for estranes over androstanes. However, also catalyzes the conversion of DHEA into androstenediol. Expressed primarily in the ovaries and placenta but also at lower levels in the breast epithelium. Major isoform of 17β-HSD in the granulosa cells of the ovaries. Mutations and associated deficiency have not been reported in humans. Knockout mice show altered ovarian sex steroid production, normal puberty, and severe subfertility due to defective luteinization and ovarian progesterone production. •
HSD17B2: Describable as "antiestrogenic" and "antiandrogenic". Major subtype for inactivation of estrogens and androgens into weaker forms (estradiol to estrone, testosterone to androstenedione, and androstenediol to DHEA). Also converts inactive
20α-hydroxyprogesterone into active progesterone. Preferential activity on androgens. Expressed widely in the body including in the liver, intestines, lungs, pancreas, kidneys, endometrium, prostate, breast epithelium, placenta, and bone. Said to be responsible for 17β-HSD activity in the endometrium and placenta. Mutations and associated congenital deficiency have not been reported in humans. •
HSD17B3: Referred to as "androgenic". Major subtype in males for activation of androgens from weaker forms (androstenedione to testosterone and DHEA to androstenediol). Also activates estrogens from weaker forms to a lesser extent (estrone to estradiol). This is essential for testicular but not ovarian production of testosterone. Not expressed in the ovaries, where another 17β-HSD subtype, likely HSD17B5, is expressed instead. Mutations are associated with
type III deficiency. Males with this condition have pseudohermaphroditism, while females are normal with normal androgen and estrogen levels. Mutations are associated with
DBP deficiency and
Perrault syndrome (ovarian dysgenesis and deafness). May be involved in the pathophysiology of . •
HSD17B9: Also known as retinol dehydrogenase 5 (RDH5). Involved in
retinoid metabolism. Mutations are associated with
fundus albipunctatus. •
HSD17B10: Also known as 2-methyl-3-hydroxybutyryl-CoA dehydrogenase (MHBD). Substrates include steroids,
neurosteroids, fatty acids,
bile acids,
isoleucine, and
xenobiotics. Mutations are associated with
type X deficiency (also known as HSD10 disease or MHBD deficiency) and
mental retardation, X-linked, syndromic 10 (MRXS10), which are characterized by
neurodegeneration and
mental retardation, respectively. •
HSD17B12 •
HSD17B13 •
HSD17B14 At least 7 of the 14 isoforms of 17β-HSD are involved in interconversion of
17-ketosteroids and
17β-hydroxysteroids.
Overview ==Clinical significance==