CYP17A1
cytochrome P450 family 17 subfamily A member 1
Gene summary
A protein-coding gene on chromosome 10 (steroid hormone synthesis). Encodes a member of the cytochrome P450 superfamily of enzymes. The cytochrome P450 proteins are monooxygenases which catalyze many reactions involved in drug metabolism and synthesis of cholesterol, steroids and other lipids.
Source: NCBI Gene, accessed 2026-10-07.
Protein reference (UniProt)
- Protein
Steroid 17-alpha-hydroxylase/17,20 lyase
- Function (excerpt)
A cytochrome P450 monooxygenase involved in corticoid and androgen biosynthesis. Catalyzes 17-alpha hydroxylation of C21 steroids, which is common for both pathways. A second oxidative step, required only for androgen synthesis, involves an acyl-carbon cleavage. The 17-alpha hydroxy intermediates, as part of adrenal glucocorticoids biosynthesis pathway, are precursors of cortisol (Probable). Hydroxylates steroid hormones, pregnenolone and progesterone to form 17-alpha hydroxy metabolites, followed by the cleavage of the C17-C20 bond to form C19 steroids, dehydroepiandrosterone (DHEA) and androstenedione. Has 16-alpha hydroxylase activity. Catalyzes 16-alpha hydroxylation of 17-alpha hydroxy pregnenolone, followed by the cleavage of the C17-C20 bond to form 16-alpha-hydroxy DHEA. Also 16-alpha hydroxylates androgens, relevant for estriol synthesis.
- Pathway
Steroid hormone biosynthesis. Steroid biosynthesis; glucocorticoid biosynthesis.
- Subcellular location
Endoplasmic reticulum membrane; Microsome membrane.
- Associated conditions
Adrenal hyperplasia 5 (AH5).
Source: UniProtKB/Swiss-Prot P05093, 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 CYP17A1 specifically.
Narrative library record
Function
Dual-function P450 enzyme with 17-alpha-hydroxylase and 17,20-lyase activities - the key branch point of steroidogenesis that diverts pregnenolone/progesterone toward glucocorticoids versus DHEA and androstenedione (androgen precursors). Expressed in adrenals, gonads, and other tissues; deficiency causes 17-hydroxylase deficiency with pseudohermaphroditism and adrenal hyperplasia.
Corpus relevance
Background-pathway gene: the gatekeeper deciding how much steroid flux becomes androgen versus glucocorticoid, hence upstream of every androgen/neurosteroid balance the corpus debates. Included to complete the pathway; no direct PFS/PSSD implication in the corpus.
Mentioned in 8 corpus records
- Powers · Reddit commentCurated Powers pick
Re: Question to Dr Powers: What is the significance of 17-hydroxyprogesterone to progesterone ratio for PFS patients?
u/drwillpowers · r/DrWillPowers
Powers said 17α-hydroxylase deficiency is one of the mutations he has seen several times in PFS genomes, with no 3β-HSD signal observed (though 3α is a different story). He reasoned such a defect would produce higher baseline progesterone in affected males…
CYP17A1PRH-02522026-08-05T17:07:58ZPFSPSSDPowers Reddit history - Gene record
Steroid-hormone-activated transcription factor (nuclear receptor subfamily 3, group C, member 4). On binding testosterone or DHT it sheds accessory proteins, moves to the nucleus, dimerizes, and switches on androgen-responsive genes. Its N-terminal domain…
AKR1C2ARCYP17A1HSD3B2SRD5A2GENE-ARPFSCore corpus - Gene record
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…
AKR1C1CYP17A1HSD3B1HSD3B2SRD5A1GENE-HSD3B1PFSPSSDCore 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 - Gene record
Aromatase - the P450 enzyme catalyzing the final steps of estrogen biosynthesis, converting androgens (testosterone, androstenedione) to estrogens (estradiol, estrone). Tissue-specific promoters drive expression in placenta, gonads, adipose, and brain…
AKR1C3ARCYP17A1CYP19A1HSD3B2GENE-CYP19A1PFSPSSDCore corpus - Gene recordPowers’ theory
Short-chain dehydrogenase/reductase (17-beta-HSD type 2) that inactivates sex steroids, oxidizing testosterone to androstenedione, estradiol to estrone, and androstenediol to DHEA; described as the key 17-beta-HSD isozyme in androgen and estrogen…
AKR1C2CYP17A1CYP19A1HSD17B2SRD5A2+1GENE-HSD17B2PFSCore corpus - Gene recordPowers’ theory
Adrenal endoplasmic-reticulum P450 (steroid 21-hydroxylase) required for cortisol and aldosterone synthesis, converting progesterone and 17-hydroxyprogesterone toward their 21-hydroxylated products; mutations are the cause of congenital adrenal hyperplasia.
CYP11A1CYP17A1CYP21A2CYP21A2PHSD3B2GENE-CYP21A2PFSCore corpus - Gene recordPowers’ theory
Mitochondrial P450 (P450scc, cholesterol side-chain cleavage enzyme) catalyzing the first, rate-limiting step of steroidogenesis - three sequential reactions converting cholesterol to pregnenolone; severe loss disrupts all adrenal and gonadal steroid…
CYP11A1CYP17A1CYP21A2HSD3B2GENE-CYP11A1PFSCore corpus
Also in steroid hormone synthesis
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chr 2· Steroid synthesis· 19 records - SRD5A1Powers
steroid 5 alpha-reductase 1
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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 - 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 - SRD5A3
steroid 5 alpha-reductase 3
chr 4· Steroid synthesis· 6 records
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