rs2414096 — CYP19A1 CYP19A1 intron 4 polymorphism

Intronic CYP19A1 polymorphism associated with variation in aromatase expression and androgen-to-estrogen conversion; the G allele is linked to lower aromatase activity and elevated androgen levels in reproductive tissues, with population-specific associations to PCOS risk

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CYP19A1 Intron 4 Variant — An Aromatase Regulator With Population-Dependent Effects on Androgen Balance

Aromatase11 Aromatase
the enzyme encoded by CYP19A1 that catalyzes the final and rate-limiting step of estrogen biosynthesis, converting androgens such as androstenedione and testosterone to estrogens is expressed in the ovaries, adipose tissue, bone, brain, and adrenal glands. Because it is the only enzyme capable of estrogen synthesis in vertebrates, even small changes in its expression can meaningfully shift the androgen–estrogen balance. The rs2414096 variant lies in intron 4 of CYP19A1 on chromosome 15 and does not alter the protein sequence, but several lines of evidence suggest it may influence aromatase expression levels or transcript regulation, with downstream effects on androgen-to-estrogen conversion.

The Mechanism

As an intronic variant, rs2414096 does not directly alter aromatase enzyme structure. Instead, it may act through effects on splicing efficiency, mRNA stability, or linkage disequilibrium with nearby regulatory elements. CYP19A1 is a complex locus with multiple tissue-specific promoters controlling aromatase expression in different organs; intronic variants can modulate these promoter activities in tissue-specific ways. The variant is located on chromosome 15 at position 51,237,582 (GRCh38), within intron 4, and CYP19A1 itself is transcribed from the minus strand22 CYP19A1 itself is transcribed from the minus strand. The GRCh38 reference allele (G) — corresponding to a C on the coding strand — appears to be the allele associated with lower aromatase activity based on multiple functional and association studies.

The Evidence

The primary evidence base consists of association studies across multiple populations, two meta-analyses, and a study linking this variant to direct hormone-level differences.

A 2021 meta-analysis of seven studies (1,414 PCOS cases, 1,276 controls) by Sharma et al.33 A 2021 meta-analysis of seven studies (1,414 PCOS cases, 1,276 controls) by Sharma et al.
CYP19 gene rs2414096 variant and differential genetic risk of polycystic ovary syndrome: a systematic review and meta-analysis. Gynecol Endocrinol 2021 found that the GG dominant model (GG+GA vs AA) was significantly associated with PCOS risk (OR=1.60, 95% CI 1.10–2.31, p=0.01), with the overall A-allele effect estimate of OR=0.74 (95% CI 0.62–0.88, p=0.0008), indicating the A allele is protective. The association was statistically significant in non-Indian populations but not Indian subpopulations, where genetic diversity is greater.

However, a larger 2022 meta-analysis by Xing et al. of 26 studies (4,860 PCOS cases, 4,043 controls)44 a larger 2022 meta-analysis by Xing et al. of 26 studies (4,860 PCOS cases, 4,043 controls)
The Association of CYP17A1, CYP19A1, and SHBG Gene Polymorphisms in Polycystic Ovary Syndrome Susceptibility. Front Physiol 2022 found no statistically significant overall association (OR=0.87, p=0.578) with extreme heterogeneity (I²=95.9%), underscoring that this variant's effects are genuinely population-dependent rather than universal.

Genotype-specific hormone data strengthen the mechanistic case. An analysis of 394 Kashmiri PCOS patients and 306 controls found that the GG genotype was associated with significantly elevated DHEAS, androstenedione, testosterone, and free androgen index55 An analysis of 394 Kashmiri PCOS patients and 306 controls found that the GG genotype was associated with significantly elevated DHEAS, androstenedione, testosterone, and free androgen index
Ashraf et al. 2021. Impact of rs2414096 polymorphism of CYP19 gene on susceptibility of polycystic ovary syndrome and hyperandrogenism in Kashmiri women. Sci Rep 2021 (all comparisons p<0.05), supporting the hypothesis that the G allele reduces aromatase-driven androgen conversion. Similarly, a South Indian study of 150 PCOS patients found GG more prevalent among cases, with elevated LH/FSH ratios in GG carriers, and concluded that GG may exhibit reduced aromatase activity with subsequent hyperandrogenism66 South Indian study of 150 PCOS patients found GG more prevalent among cases, with elevated LH/FSH ratios in GG carriers, and concluded that GG may exhibit reduced aromatase activity with subsequent hyperandrogenism
Hegde et al. 2023. Delineating the role of single-nucleotide polymorphism of CYP19 gene on aromatase activity in South Indian women with PCOS. J Genet Eng Biotechnol 2023.

On the question of circulating hormones, the SWAN study of 1,538 multiethnic midlife women found that Caucasian women with the AA genotype had markedly lower SHBG levels after adjusting for age and BMI77 the SWAN study of 1,538 multiethnic midlife women found that Caucasian women with the AA genotype had markedly lower SHBG levels after adjusting for age and BMI
Sowers et al. 2006. Aromatase gene (CYP 19) polymorphisms and endogenous androgen concentrations in a multiracial/multiethnic, multisite study of women at midlife. Am J Med 2006. Lower SHBG increases free testosterone bioavailability, which may appear directionally contradictory to the PCOS data above — it suggests AA carriers have higher free androgen exposure despite a proposed protective effect on PCOS. This likely reflects tissue-specific or context-specific aromatase regulation: ovarian aromatase activity and circulating SHBG regulation are influenced by different promoters and feedback mechanisms. Context matters, and a single intronic variant almost certainly does not have a unidirectional effect across all tissues simultaneously.

Practical Actions

For women with PCOS features — irregular cycles, hirsutism, elevated androgens, or anovulatory infertility — the GG genotype adds a modest piece of evidence supporting impaired androgen-to-estrogen conversion in the ovary. This reinforces evaluation of androgen levels alongside this genotype, and consideration of aromatase-relevant interventions when clinically appropriate. Letrozole (an aromatase inhibitor paradoxically used to stimulate ovulation in PCOS by briefly lowering estrogen feedback, prompting FSH surge) is the standard-of-care first-line ovulation induction agent in PCOS; whether this genotype modifies letrozole response is an open question with no prospective pharmacogenomic data yet.

The heterogeneous evidence means this variant should be interpreted in the context of clinical findings, not used as a standalone diagnostic marker.

Interactions

Rs2414096 is part of the CYP19A1 locus alongside rs700518 (Val80, synonymous variant affecting aromatase expression and AI side-effect risk), rs700519 (Arg264Cys, coding variant with increased catalytic activity in vitro), and rs1062033 (intronic regulatory variant with CEBPβ-mediated transcriptional effect on aromatase in bone). These variants form haplotypes and may have compounded effects on total aromatase expression and activity — their combined influence on androgen–estrogen balance in reproductive tissues, bone, and adipose tissue is likely greater than any individual variant's effect alone. Women carrying risk genotypes across multiple CYP19A1 loci may have a broader pattern of altered estrogen synthesis worth evaluating with comprehensive hormone panels.

Genotype Interpretations

What each possible genotype means for this variant.

AA Higher Aromatase Activity Beneficial

Two copies of the A allele; associated with higher aromatase expression and more efficient androgen-to-estrogen conversion in reproductive tissues

You have two copies of the A allele at rs2414096. This genotype is associated with more efficient aromatase-driven androgen conversion in reproductive tissues based on association data from multiple PCOS case-control studies. In the Sharma et al. 2021 meta-analysis, carrying two A alleles (AA) was associated with the lowest PCOS risk compared with GG or GA genotypes (dominant model OR=1.60 for GG+GA vs AA). The AA genotype accounts for roughly 21% of the global population, and is somewhat less common than would be expected in European populations based on allele frequency (~22% by Hardy-Weinberg, consistent with global estimates).

Note that the larger Xing et al. 2022 meta-analysis found no overall PCOS association with high heterogeneity, meaning this interpretation applies most reliably in populations where the association has been replicated (particularly non-Indian populations). One SWAN study finding — lower SHBG in Caucasian AA women — is directionally paradoxical and may reflect tissue-specific or hormonal-context-specific aromatase regulation distinct from the ovarian PCOS pathway.

AG Intermediate Aromatase Activity Intermediate

Carrier of one G allele; intermediate aromatase activity with modest evidence for mild androgen excess tendency in some populations

You carry one copy of the G allele (risk allele) and one copy of the A allele. This heterozygous genotype is the most common globally, found in approximately 50% of people. The dominant-model meta-analysis by Sharma et al. 2021 grouped this genotype with GG homozygotes (GG+GA vs AA; OR=1.60 for PCOS), suggesting that even one copy of the G allele confers some elevation in PCOS-associated risk compared to AA — though the evidence is population-dependent and the larger Xing 2022 meta-analysis found no overall association.

For most people with this genotype, no clinical action is warranted without corroborating clinical or hormonal findings.

GG Lower Aromatase Activity High Risk

Two copies of the G allele; associated with reduced aromatase activity in the ovary and elevated androgen levels in multiple PCOS case-control studies

You have two copies of the G allele at rs2414096. In the Sharma et al. 2021 meta-analysis of seven PCOS studies (1,414 cases, 1,276 controls), the GG genotype was associated with the highest PCOS risk (dominant model OR=1.60 for GG+GA vs AA). Functional studies in South Indian and Kashmiri women with PCOS found GG carriers had significantly elevated androgens — including DHEAS, androstenedione, testosterone, and free androgen index — compared with A allele carriers, consistent with reduced aromatase-driven conversion of androgens to estrogens in the ovary.

This genotype accounts for approximately 29% of the global population but varies widely: lower in Europeans (~22%) and higher in African (~64%) and South Asian (~44%) populations. The association with PCOS is most consistently reported in non-Indian populations; a larger 26-study meta-analysis found no overall significant association, reflecting genuine population heterogeneity. Interpret alongside clinical features rather than in isolation.