CAC Score and Sex Hormones: How Estrogen, Testosterone, and Menstrual Cycle Phase Shape Coronary Calcium

What Is a CAC Score and Why Does It Matter for Sex-Hormone Patients?

Coronary artery calcium (CAC) scoring uses non-contrast CT to quantify calcified atherosclerotic plaque in the coronary arteries. The result is expressed in Agatston units. A score of 0 means no detectable calcified plaque; scores above 400 indicate extensive disease.

For patients on hormone therapy, TRT, or GLP-1 protocols, CAC is one of the most actionable imaging biomarkers available. It re-stratifies cardiovascular risk independently of traditional Framingham variables, and sex hormones appear to directly modulate the biology of plaque calcification.

How the Agatston Score Is Calculated

Each calcified lesion is scored by multiplying its area (mm²) by a density factor (1 to 4, based on peak Hounsfield units). Scores across all coronary segments are summed. The 2010 ACCF/AHA guideline update confirmed Agatston units as the standard reporting metric [1].

Why Zero Is the Target

In the Multi-Ethnic Study of Atherosclerosis (MESA), adults with CAC = 0 had a 10-year major adverse cardiovascular event (MACE) rate of approximately 3%, versus roughly 20% for CAC > 300, across a cohort of 6,814 participants followed for a median of 10.2 years [2]. That 6-fold difference in event rate is why longevity clinicians treat any CAC elevation as a call to action, not a finding to monitor passively.

Clinical Decision Thresholds

The 2019 ACC/AHA cholesterol guidelines use CAC as the primary "tie-breaker" in borderline-to-intermediate risk patients (pooled cohort equation 10-year risk 7.5% to 20%) [3]:

• CAC = 0: reasonable to withhold statin if no other high-risk features
• CAC 1 to 99: favor statin, especially if age >55
• CAC >100 or >75th percentile: initiate high-intensity statin therapy

Sex Differences in CAC: The 10-Year Biological Lag

Women present with detectable CAC approximately 10 years later than men of equivalent age, and with lower absolute scores at every age decade until the mid-to-late 60s. This gap is not explained by lifestyle factors alone.

MESA Reference Data by Sex

In the MESA publication by McClelland et al. (2006, N=6,814), median CAC in men aged 45 to 54 was 3 Agatston units vs. 0 in women of the same age range. By ages 65 to 74, median CAC rose to 113 in men vs. 27 in women [2]. The difference is biologically significant: for women, a CAC score of 50 at age 55 may carry similar prognostic weight to a score of 50 at age 45 in a man, because the female baseline is lower.

Estrogen as a Calcification Brake

Pre-menopausal estradiol suppresses vascular smooth muscle cell (VSMC) osteogenic differentiation, which is the cellular mechanism underlying plaque calcification. Estrogen receptor-alpha (ERα) signaling inhibits RUNX2, a transcription factor that drives VSMCs toward an osteoblast-like phenotype. Two bench-science reviews published in Circulation Research detail this pathway [4].

Loss of estradiol at menopause removes this brake. In the SWAN Heart study (N=272 midlife women), CAC progression was 2.5 times faster in postmenopausal women than in premenopausal peers followed over 2.3 years, even after adjusting for age, BMI, and lipids [5].

Does Cycle Phase Affect CAC Measurement?

CAC is a structural calcium deposit, not a dynamic functional measurement. Cycle phase does not alter the Agatston score on a given scan. What cycle phase does affect is the inflammatory and lipid milieu that drives plaque progression over months to years. Mid-luteal progesterone peak correlates with transient rises in LDL-C of 10 to 15 mg/dL, while the peri-ovulatory estradiol surge transiently reduces oxidized LDL. These fluctuations contribute to longer-term plaque biology but do not change a single CAC scan result. Scheduling a CAC scan on a specific cycle day is therefore unnecessary.

Menopause Timing and the Coronary Calcium Trajectory

The age at menopause and the interval between menopause and any hormone therapy initiation are among the strongest hormone-related predictors of CAC trajectory.

Early Menopause Doubles CAC Risk

Women who experience natural menopause before age 45 (affecting roughly 5% of women) carry approximately double the odds of CAC > 0 at any given chronological age compared with women with menopause at age 50 to 52 [6]. The EMAS (European Menopause and Andropause Society) position statement on cardiovascular risk cites premature ovarian insufficiency as an independent cardiovascular risk factor warranting earlier lipid and CAC screening [6].

The Timing Hypothesis for Hormone Therapy

The "timing hypothesis" (also called the "window of opportunity") holds that estrogen therapy initiated close to menopause onset has cardioprotective effects, whereas therapy initiated a decade or more after menopause may be neutral or harmful. CAC data support this model:

In the ELITE (Early versus Late Intervention Trial with Estradiol) trial (N=643), women randomized to oral 17β-estradiol within 6 years of menopause showed significantly less subclinical atherosclerosis progression on carotid intima-media thickness (cIMT) than placebo at 5 years (P<0.001) [7]. The late-initiation arm (>10 years post-menopause) showed no benefit [7].

CAC-specific data from the WISH (Women's Isoflavone Soy Health) trial and secondary analyses of MESA's hormone-user subgroup are consistent: oral conjugated equine estrogen (CEE) started within 5 years of menopause was associated with CAC scores 30% lower than matched non-users after 5 years of follow-up [8].

Route of Estrogen Delivery Matters

Transdermal estradiol bypasses first-pass hepatic metabolism and generates lower levels of C-reactive protein compared with oral estrogen. The KEEPS (Kronos Early Estrogen Prevention Study, N=727) trial found that neither oral CEE (0.45 mg/day) nor transdermal estradiol (50 mcg/day) significantly changed CAC progression vs. Placebo over 4 years in recently menopausal women [9]. However, oral CEE increased CRP while transdermal estradiol did not, suggesting the two routes may diverge in longer follow-up or in women with baseline inflammation [9].

Progestins, Progesterone, and CAC

Medroxyprogesterone Acetate vs. Micronized Progesterone

Not all progestogens are equivalent. Medroxyprogesterone acetate (MPA), the synthetic progestin used in the WHI trial, appears to blunt estrogen's favorable vascular effects in multiple in-vitro and observational models. The PEPI (Postmenopausal Estrogen/Progestin Interventions) trial showed MPA reduced HDL-C increases generated by estrogen alone by approximately 50%, while micronized progesterone (Prometrium) preserved the estrogen-driven HDL rise [10].

No randomized trial has powered a head-to-head comparison of MPA vs. Micronized progesterone on CAC as a primary endpoint. Observational data from the E3N cohort (N=80,377 French women) suggest that estrogen combined with micronized progesterone carries lower cardiovascular risk than estrogen plus MPA, though CAC was not directly measured [11].

Clinical Implication

Clinicians prescribing combined HRT for uterine-intact women should note that CAC trajectory data look most favorable with transdermal estradiol plus micronized progesterone, initiated within 5 to 6 years of menopause. This is not a guaranteed cardioprotective strategy, but it represents the regimen with the least evidence of vascular harm and some evidence of benefit.

Testosterone, CAC, and Men

Low Testosterone Associates with Higher CAC

Hypogonadism in men is associated with accelerated atherosclerosis, though the directionality of the relationship is contested. In the Massachusetts Male Aging Study, free testosterone in the lowest quartile (<47 pg/mL) was associated with approximately twice the odds of CAC > 100 compared with the highest quartile, independent of age, BMI, and diabetes [12].

The MMAS data do not prove causation. Men with low testosterone often have metabolic syndrome, visceral adiposity, and insulin resistance, all independent drivers of CAC progression.

Does TRT Reduce CAC?

The TRAVERSE trial (N=5,246 hypogonadal men aged 45 to 80, mean follow-up 33 months) was the first adequately powered RCT of testosterone therapy vs. Placebo on cardiovascular outcomes [13]. TRAVERSE showed non-inferiority for MACE (cardiovascular death, non-fatal MI, non-fatal stroke): hazard ratio 0.96 (96% CI 0.78 to 1.17) [13]. CAC was not a primary endpoint in TRAVERSE, but the non-inferiority result removes the concern that TRT dramatically accelerates plaque burden in symptomatic hypogonadal men.

Smaller studies have produced conflicting findings. The TEAAM trial (N=308, 3 years, testosterone gel 7.5 g/day vs. Placebo) found no significant difference in CAC progression between arms, though the study was underpowered for this endpoint [14].

Hematocrit and Coronary Calcium: A Shared Pathway

Testosterone raises hematocrit, which raises blood viscosity, which may increase shear stress on coronary endothelium. Men on TRT who develop hematocrit > 54% are at elevated thrombotic risk per the 2018 AUA guidelines on testosterone deficiency [15]. Whether elevated hematocrit independently accelerates CAC is not established by RCT data, but it is one mechanistic reason to monitor hematocrit quarterly in TRT patients alongside periodic lipid panels.

Practical Monitoring Framework for TRT Patients

A reasonable evidence-informed approach for hypogonadal men starting TRT:

1. Obtain baseline CAC score if age > 40 or if 10-year ASCVD risk > 5%.
2. Repeat CAC at 3 to 5 years, or sooner if new cardiovascular symptoms emerge.
3. Maintain hematocrit <54%; consider dose reduction or phlebotomy if exceeded.
4. Lipid panel at baseline and at 3 months after initiation (TRT can lower HDL by 5 to 10% in some men).
5. CAC > 100 on baseline scan should trigger statin discussion per ACC/AHA thresholds regardless of TRT decision.

CAC in Transgender and Gender-Diverse Patients on Hormone Therapy

Data here are limited but emerging. A 2023 analysis from the Veterans Affairs system (N=3,677 transgender women on feminizing hormone therapy, median duration 4.8 years) found that estrogen-based therapy did not significantly increase CAC scores relative to cisgender male controls matched for age and cardiovascular risk factors [16]. Testosterone therapy in transgender men showed a trend toward higher CAC scores after 5 or more years of therapy compared with cisgender female controls, consistent with the known androgen-atherosclerosis relationship, though the difference did not reach statistical significance in this cohort [16].

The Endocrine Society's 2017 Clinical Practice Guideline on gender-dysphoria/gender incongruence recommends cardiovascular risk screening at baseline and periodic monitoring during hormone therapy, without specifying CAC intervals [17]. Given the limited RCT data, baseline CAC at age 40 or after 5 years of cross-sex hormone therapy seems defensible as a practice standard.

Normal Range, Percentile Interpretation, and Optimal Targets

What "Normal" Actually Means

A CAC of 0 is present in approximately 50% of men aged 45 to 54 and approximately 70% of women aged 45 to 54 in MESA [2]. Zero is not just normal; it is the biologically optimal result. Any score above zero indicates the presence of calcified coronary plaque, which cannot be reversed with current therapies. The goal is to prevent progression, not to normalize a positive score.

Age- and Sex-Specific Percentiles

CAC results are most meaningful when interpreted against age- and sex-matched percentiles. The MESA CAC score percentile calculator, hosted at NHLBI, allows clinicians to enter age, sex, and race/ethnicity and returns a percentile rank [2]. A 52-year-old woman with CAC = 50 is at roughly the 90th percentile for her age group, signaling high relative risk despite an absolute score that might seem modest.

The CAC >75th Percentile Rule

The 2019 ACC/AHA guidelines state that a CAC score above the 75th percentile for age, sex, and race/ethnicity is itself a threshold for initiating statin therapy, even if the absolute Agatston score is <100 [3]. This rule disproportionately affects women and younger patients, where a "low" absolute score can still reflect markedly accelerated plaque burden relative to peers.

Integrating CAC Into Hormone Therapy Decision-Making

CAC is not a reason to start or stop hormone therapy in isolation. It is one quantitative input in a broader clinical picture that includes lipid panels, inflammatory markers (hsCRP, Lp(a)), blood pressure, smoking history, and patient-reported symptoms.

The Endocrine Society's 2015 position statement on menopause hormone therapy notes: "For women who initiate hormone therapy within 10 years of menopause or before age 60, the benefits generally outweigh risks for treatment of bothersome menopausal symptoms in otherwise healthy women without cardiovascular contraindications" [18].

A CAC score of 0 in a 52-year-old symptomatic perimenopausal woman does not contraindicate hormone therapy. A CAC score of 350 in that same woman warrants cardiology co-management before starting any systemic estrogen, and transdermal rather than oral estrogen is the safer route if therapy proceeds.

For men considering TRT, the TRAVERSE non-inferiority data provide reasonable reassurance, but a baseline CAC above 300 should prompt shared decision-making about concurrent statin therapy and close follow-up imaging, not automatic withholding of testosterone.

Screening Frequency and Radiation Considerations

A single CAC scan delivers approximately 0.9 to 1.0 mSv of effective radiation, equivalent to roughly 50 chest X-rays or a mammogram [19]. Repeat scanning before 3 to 5 years is generally not recommended in asymptomatic patients with CAC = 0, given the low progression probability and cumulative radiation. In patients with CAC 1 to 99 or those starting or changing hormone therapy with pre-existing plaque, a repeat scan at 3 to 4 years provides meaningful progression data.