HSD3B1
hydroxy-delta-5-steroid dehydrogenase, 3 beta- and steroid delta-isomerase 1
Gene summary
A protein-coding gene on chromosome 1 (steroid hormone synthesis). The protein encoded by this gene is an enzyme that catalyzes the oxidative conversion of delta-5-3-beta-hydroxysteroid precursors into delta-4-ketosteroids, which leads to the production of all classes of steroid hormones. The protein also catalyzes the interconversion of 3-beta-hydroxy- and 3-keto-5-alpha-androstane steroids.
Source: NCBI Gene, accessed 2026-10-07.
Protein reference (UniProt)
- Protein
3 beta-hydroxysteroid dehydrogenase/Delta 5-->4-isomerase type 1
- Function
A bifunctional enzyme responsible for the oxidation and isomerization of 3beta-hydroxy-Delta(5)-steroid precursors to 3-oxo-Delta(4)-steroids, an essential step in steroid hormone biosynthesis. Specifically catalyzes the conversion of pregnenolone to progesterone, 17alpha-hydroxypregnenolone to 17alpha-hydroxyprogesterone, dehydroepiandrosterone (DHEA) to 4-androstenedione, and androstenediol to testosterone. Additionally, catalyzes the interconversion between 3beta-hydroxy and 3-oxo-5alpha-androstane steroids controlling the bioavalability of the active forms. Specifically converts dihydrotestosterone to its inactive form 5alpha-androstanediol, that does not bind androgen receptor/AR. Also converts androstanedione, a precursor of testosterone and estrone, to epiandrosterone. Expected to use NAD(+) as preferred electron donor for the 3beta-hydroxy-steroid dehydrogenase activity and NADPH for the 3-ketosteroid reductase activity (Probable).
- Pathway
Steroid hormone biosynthesis. Steroid metabolism.
- Subcellular location
Endoplasmic reticulum membrane; Mitochondrion membrane.
- Tissue specificity
Placenta and skin. Predominantly expressed in mammary gland tissue.
Source: UniProtKB/Swiss-Prot P14060, release 2026_03, licensed CC BY 4.0. This is the protein’s normal biology, not evidence about post-drug syndromes; associated conditions are inherited disorders of the gene, not PFS, PSSD or PRSD.
Why its pathway is in the library
Steroid-synthesis enzymes sit directly on the pathways perturbed by 5-alpha-reductase inhibitors and SSRIs; inherited variation here is a candidate susceptibility factor for persistent post-drug phenotypes.
Written for the whole steroid synthesis family, not for HSD3B1 specifically.
Narrative library record
Function
Bifunctional enzyme oxidizing delta-5-3-beta-hydroxysteroids and isomerizing them to delta-4-ketosteroids - an essential step in making all classes of active steroid hormones. HSD3B1 is expressed in placenta and peripheral tissues (critical for placental progesterone production).
Corpus relevance
Background-pathway gene: sits upstream of progesterone/allopregnanolone synthesis, the neurosteroid axis at the heart of both Powers' models and the Melcangi CSF studies (PFS-004, PFS-005). Included to complete the steroidogenic pathway map; not directly implicated in any corpus PFS/PSSD finding.
- PFS-004Neuroactive steroid levels are modified in cerebrospinal fluid and plasma of post-finasteride patients showing persistent sexual side effects and anxious/depressive symptomatology
- PFS-005Patients treated for male pattern hair with finasteride show, after discontinuation of the drug, altered levels of neuroactive steroids in cerebrospinal fluid and plasma
- PFS-0115α-Reductase Isoenzymes: From Neurosteroid Biosynthesis to Neuropsychiatric Outcomes
Mentioned in 2 corpus records
- Gene record
3-oxo-5-alpha-steroid 4-dehydrogenase 1; converts testosterone to the more potent DHT and reduces progesterone, corticosterone, and other steroids via 5-alpha-reduction (hydride transfer from NADPH to carbon 5). Also active in bile-acid biosynthesis; broadly…
AKR1C2HSD3B1SRD5A1SRD5A2SRD5A3GENE-SRD5A1PFSCore corpus - Gene record
The adrenal/gonadal isoform of 3-beta-HSD, predominantly expressed in adrenals, ovaries, and testes; catalyzes the same essential delta-5-to-delta-4 steroid conversion. Deficiency causes a rare congenital adrenal hyperplasia.
CYP17A1CYP19A1HSD3B1HSD3B2SRD5A2GENE-HSD3B2PFSPSSDCore corpus
Also in steroid hormone synthesis
All 38 genes- SRD5A2
steroid 5 alpha-reductase 2
chr 2· Steroid synthesis· 19 records - SRD5A1Powers
steroid 5 alpha-reductase 1
chr 5· Steroid synthesis· 17 records - AKR1C2Powers
aldo-keto reductase family 1 member C2
chr 10· Steroid synthesis· 12 records - AKR1C3Powers
aldo-keto reductase family 1 member C3
chr 10· Steroid synthesis· 9 records - CYP17A1
cytochrome P450 family 17 subfamily A member 1
chr 10· Steroid synthesis· 9 records - AKR1C4Powers
aldo-keto reductase family 1 member C4
chr 10· Steroid synthesis· 8 records - AKR1C1Powers
aldo-keto reductase family 1 member C1
chr 10· Steroid synthesis· 7 records - HSD3B2
hydroxy-delta-5-steroid dehydrogenase, 3 beta- and steroid delta-isomerase 2
chr 1· Steroid synthesis· 7 records
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