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Published on: August 13, 2019

Hormone replacement therapy: prothrombotic vs. protective effects

Gordon D O Lowe1

  • 1Department of Medicine, Royal Infirmary, University of Glasgow, UK. gdl1j@clinmed.gla.ac.uk

Pathophysiology of Haemostasis and Thrombosis
|September 26, 2003
PubMed

Insights

Hormone replacement therapy (HRT) may increase risks for heart attack and blood clots, especially with oral forms. Ongoing trials are clarifying the balance of risks and benefits for women.

Area of Science:

  • Cardiovascular Medicine
  • Endocrinology
  • Pharmacology

Background:

  • Observational studies suggest hormone replacement therapy (HRT) reduces coronary heart disease (CHD) and stroke risk.
  • Confounding factors in observational studies necessitate randomized controlled trials for accurate risk-benefit assessment of HRT.

Purpose of the Study:

  • To prospectively assess the risks and benefits of hormone replacement therapy (HRT) in secondary prevention of coronary heart disease (CHD).
  • To evaluate the prothrombotic and protective effects of various HRT preparations.

Main Methods:

  • Analysis of data from the HERS trial (Heart and Estrogen-Replacement Study) on oral HRT in secondary CHD prevention.
  • Review of prospective and case-control studies examining HRT's association with venous thromboembolism (VTE) and myocardial infarction (MI).
  • Assessment of HRT's impact on hemostatic factors, lipids, blood pressure, and endothelial function.

Main Results:

  • The HERS trial indicated an early increased risk of myocardial infarction (MI) and venous thromboembolism (VTE) with oral HRT.
  • A history of VTE or MI is now a contraindication for oral HRT.
  • Oral HRT may increase prothrombotic factors (e.g., factors VII, IX) and decrease antithrombotic factors, while transdermal HRT may have different effects.

Conclusions:

  • Oral HRT presents an increased risk of MI and VTE, particularly in women with existing cardiovascular conditions.
  • The balance of prothrombotic and protective effects of HRT is variable and depends on the preparation and individual patient factors.
  • Ongoing large randomized trials are crucial for a comprehensive understanding of HRT's cardiovascular risks and benefits.

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