Hormone Therapy Pills Linked to Increased Blood Clot Risk
A new study indicates that oral hormone replacement therapy, even at low doses and for short durations, may elevate the risk of potentially fatal blood clots.
Oral hormone replacement therapy (HRT) pills are associated with a 60% increased risk of venous thromboembolism, commonly known as blood clots, according to a large-scale study.
The research, published in the British Medical Journal, analyzed health registry data from over one million Danish women aged 50 to 69 between 2003 and 2021. Scientists identified associations between HRT prescriptions, including dosage and duration, and the incidence of serious blood clots, strokes, and heart attacks.
Oral HRT was linked to a higher rate of blood clots for both estrogen-only treatments and those combining estrogen with progestogen. The study suggests that this risk exists even when taking pills for less than a year or at low daily doses below 1mg.
Previous research has indicated that when estrogen is ingested, it can increase the production of blood-clotting proteins in the liver. In contrast, transdermal treatments like skin patches, gels, and sprays, which bypass the liver, do not appear to carry the same danger, the study authors concluded.
For women on high-dose oral HRT, the risk of heart attack increased by 40% and the risk of stroke by 50%. These risks could rise to 80% for those using oral HRT for more than five years. The study found that the elevated risk of blood clots was similar for women using oral HRT for under a year compared to those using it for over five years.
Experts emphasized the importance of managing cardiovascular risk factors in individuals using oral HRT and highlighted the superior safety profile of transdermal treatments over oral forms. HRT is commonly prescribed to alleviate menopausal symptoms such as hot flashes and may also offer benefits in preventing osteoporosis and potentially dementia.