byQueen Mary, University of London

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A study led by researchers at Queen Mary University of London has found that hormone replacement therapy (HRT) may help reverse changes in the immune system caused by menopause, potentially boosting immune health. The research reveals new evidence that menopause significantly alters women's immune system, increasing their vulnerability to infections.

The study,publishedinAging Cell, is the first detailed analysis of how aging and sex differences influence monocytes, a key group of immune cells that act as the body's first responders to infection.

Analyzingblood samplesfrom younger adults less than 40 years of age andolder adultsaged 65 and above, the team found that aftermenopause, women develop more inflammatory types of white blood cells called monocytes, which are less effective at clearing bacteria.

These changes were linked to lower levels of complement C3, an immune protein that helps monocytes engulf and destroy harmful microbes. In contrast, men of the same age did not show these changes, suggesting menopause has a uniquely disruptive effect on female immunity.

To test whether hormone therapy could influence this decline, the researchers studied peri- and post-menopausal women taking HRT. They found that these women had healthier immune profiles, with fewer inflammatory monocytes and stronger infection-fighting ability as compared to age-matched controls. Levels of complement C3 in their blood were also higher in those taking HRT, bringing them close to the immune status of younger women.

Dr. Emma Chambers, senior lecturer in immunology at Queen Mary and lead author of the study, said, "Our findings highlight menopause as a critical turning point for women's immunity. While aging affects everyone, the loss of female hormones appears to accelerate immune decline in women. Encouragingly,hormone therapyseems to restore key aspects of immune health, offering benefits that go beyond easing menopausal symptoms."

Menopause typically occurs in women between the ages of 45 and 55 and is often preceded by a decade-long peri-menopausal phase. Symptoms such as hot flashes,joint pain, fatigue and brain fog can have a profound effect on quality of life.

In the UK alone, more than four million women are in this age bracket, and women over 50 make up a growing proportion of the workforce. Yet they are also among the most likely to experience work disruption due tomenopausal symptoms.

HRT is already prescribed to manage symptoms, but this study suggests it may also help maintainimmune healthand reduce infection risk in later life.

The researchers caution, however, that more work is needed to confirm whether HRT reduces real-world infection rates, and to understand how different formulations or delivery methods affect the immune system.

More information: R. P. H. De Maeyer, et al. Age-Associated Inflammatory Monocytes Are Increased in Menopausal Females and Reversed by Hormone Replacement Therapy, Aging Cell (2025). DOI: 10.1111/acel.70249 Journal information: Aging Cell

Provided by Queen Mary, University of London