Low testosterone/estradiol ratio associated with higher CV risk in men with atherosclerotic disease

30/07/2018

The testosterone/estradiol ratio reflects both systemic and plaque inflammation in men undergoing carotid endarterectomy. Low ratio was associated with higher MACE risk, especially in overweight men.

Testosterone to estradiol ratio reflects systemic and plaque inflammation and predicts future cardiovascular events in men with severe atherosclerosis.
Literature - Koeverden ID, de Bakker M, Haitjema S et al. - Cardiovasc Res 2018. cvy188, https://doi.org/10.1093/cvr/cvy188

Introduction and methods

Low testosterone levels are associated with an increased risk of atherosclerotic manifestations in men [1,2], and studies have shown that an imbalanced testosterone/estradiol (T/E2) ratio can contribute to CVD progression in men [3,4]. However, these findings have been obtained in small studies or animal models and remain to be established in larger cohort studies focusing on the effect of these sex hormones on CVD in patients.

This sub-analysis of the Athero-Express Biobank Study investigated the effect of the sex hormones testosterone and estradiol on atherosclerotic plaques and cardiovascular (CV) events in 611 men with carotid endarterectomy (CEA), by calculating T/E2 ratios around time of surgery, and by analyzing histologic plaque characteristics (n=500) and inflammatory biomarkers in the blood (n=611) during a follow-up of three years.

The T/E2 was calculated by the formula: testosterone/(10*estradiol) and patients were classified based on low and high ratios. Atherosclerotic plaque samples (n=500) and patient characteristics (from the Utrecht Patient-Oriented Database (UPOD)) were collected between 2002 and 2016. CV events and/or hospitalization were addressed by questionnaires and validated by using hospital data systems. Major adverse cardiovascular event (MACE) was defined as myocardial infarction (MI), stroke or CV death (fatal MI, fatal stroke, fatal ruptured abdominal aneurysma, fata heart failure or sudden death).

Main results

Patient characteristics

  • Low T/E2 ratio was defined as Q1: <0.9878 (n=152) and Q2; 0.9878 – 1.4191 (n=153), and high T/E2 ratio was defined as Q3; 1.4192 – 1.8916 (n=153) and Q4; >1.8916 (n=153).
  • Mean testosterone and estradiol concentrations were 12.3 nmol/L (SD±5.56) and 92.8 pmol/L (SD±38.44), respectively.
  • Low T/E2 ratio was significantly associated with BMI ≥25 (P<0.001).

Blood levels and plaque characteristics

  • Lower T/E2 ratio was significantly associated with higher C-reactive protein levels (2.81 μg/mL vs. 1.22 μg/mL p<0.001) and leucocytes (8.98*109/L vs. 7.75*109/L , p=0.001) in blood.
  • A negative association was found between T/E2 ratio and the amount of neutrophils (B=-0.366; p=0.012), plaque calcification (OR: 0.816; p=0.044), interleukine-6 (IL-6) (B=-0.15 p=0.009) and IL-6 receptor (B=-0.13; p=0.024) in the atherosclerotic plaque.

Clinical outcome

  • 72 patients (11.8%) experienced a major CV endpoint during a mean follow-up of 2.7 years.
  • 6.5% suffered from stroke, 2.9% endured a MI and in total 3.9% died due to CV causes.
  • After adjustments T/E2 ratio was an independent predictor for major CV events (HR low T/E2 ratio: 1.67, 95%CI: 1.02-2.76, p=0.043).
  • Low T/E2 ratio was associated with increased stroke incidence during follow-up (HR: 2.09, 95%CI: 1.06-4.14, p=0.034).
  • BMI showed a significant interaction with the association between T/E2 ratio and MACE. HR of T/E2 ratio for MACE was higher in those with BMI ≥25 (HR: 2.42, 95%CI: 1.09-5.38, p=0.030), compared to BMI <25 (no longer statistically significantly elevated HR).

Conclusion

In men with atherosclerotic disease, low T/E2 ratio was associated with increased systemic inflammation, inflammatory proteins in the plaque, and a higher risk of major CV events in future, compared to high T/E2 ratio. The effects are largest in men with higher BMI. These findings expand the evidence on how hormonal dysbalance is associated with inflammation and vascular function, and ultimately poor outcomes. Normalizing T/E2 may play a role in secondary prevention of CVD in men.

References

1 Araujo AB, Dixon JM, Suarez E a, Murad MH, Guey LT, Wittert G a. Clinical review: Endogenous testosterone and mortality in men: a systematic review and metaanalysis. The Journal of clinical endocrinology and metabolism 2011;96:3007–3019.

2 Chan YX, Knuiman MW, Hung J, Divitini ML, Beilby JP, Handelsman DJ, Beilin J, McQuillan B, Yeap BB. Neutral associations of testosterone, dihydrotestosterone and estradiol with fatal and non-fatal cardiovascular events, and mortality in men aged 17–97 years. Clinical Endocrinology 2016;85:575–582.

3 Zheng HY, Li Y, Dai W, Wei CD, Sun KS, Tong YQ. Imbalance of testosterone/estradiol promotes male CHD development. Bio-Medical Materials and Engineering 2012;22:179–185

4 Cui Y, Dai W, Li Y. Circulating levels of sgp130 and sex hormones in male patients with coronary atherosclerotic disease. Atherosclerosis Elsevier Ltd; 2017;266:151–157.

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