Female sex hormone could offer protection against Covid, says study by King’s College London

The researchers, who studied around 6 lakh women for 5 weeks, also found that women who took contraceptive pills had a lower predicted rate of Covid.

A medic collects swab from the mouth of a woman resident for COVID-19 test in a containment zone at Kurla, Mumbai (representational image) | PTI

New Delhi: Since the beginning of the Covid-19 pandemic, studies have said that men are likely to be more susceptible to Covid-19 than women.

Now a pre-print study, conducted by King’s College London, has suggested that this could be because higher levels of estrogen — one of the female sex hormones — might offer some protection against the novel coronavirus infection.

Researchers arrived at the hypothesis after combining studies from past epidemics like SARS (SARS-CoV) and MERS with the new findings.

This theory was highlighted in animal model studies of previous coronavirus outbreaks — SARS and MERS — which suggested that variations in the severity of Covid symptoms based on age and sex could be due to a protective effect of the female sex hormone estrogen. 

“Females have shown an ability to mount a stronger immune response to a variety of viral infections because of more robust humoral and cellular immune,” the study stated. 

Researchers also examined data from a UK-wide Covid-19 Symptom Tracker app, with their focus being on how prevalent Covid was in post-menopausal women, pre-menopausal women, women who used oral contraceptive pills, and post-menopausal women who used hormone replacement therapy (HRT), in a five week period spanning 7 May to 15 June. 

Findings of the study 

The study analysed around 6,00,000 women. The researchers examined menopausal status, usage of Combined Oral Contraceptive Pills (COCP) and HRT, and Covid symptoms.

The study found that post-menopausal women, specifically in the 45-50 age group, had a higher rate of predicted Covid-19 than other studied women, and reported symptoms of anosmia (loss of sense of smell), fever and a persistent cough, and the need for oxygen treatment in the hospital. 

Post-menopausal women in the 50-65 years age group that used HRT had a higher predicted Covid-19 risk, but without the need for hospitalisation, the study said.

Women using COCP in the age group of 18-45 years had a lower predicted rate of Covid-19 and reduced frequency of symptoms, including persistent cough, delirium, anosmia, skipped meals, severe fatigue and pain.

COCP are known to contain low doses of estrogen and progesterone hormones, similar to those naturally produced by the body.

Estrogen, contraceptives and Covid

Estrogen and progesterone are the two main sex hormones that characterise women. The male body too has estrogen and progesterone, but in smaller amounts. 

Estrogen interacts with the immune system in different ways, including influencing how many immune cells are produced and how they respond to infection. It functions by binding to specific receptors, which activate processes that result in the control of many systems and functions in the body. 

This essentially means that men generate weaker immune responses and, as a consequence, are more susceptible to infectious bacteria in comparison to women. 

Progesterone can also potentially prevent harmful overreactions of the immune system as it has anti-inflammatory properties. 

SARS studies in female mice showed that blocking or removing estrogen increased the number of inflammatory cells in the animals’ lungs, making them more likely to suffer severe effects of the disease. 

Researchers in Wuhan had measured the estrogen levels of patients admitted to hospital with Covid-19 and found that women with low estrogen levels tended to have more severe Covid-19 than women with higher levels of the hormone.

The New York Times had reported in April that doctors began treating patients with estrogen in order to increase their immunity. 

What doctors say about the study

Mumbai-based gynaecologist Dr Nikhil Datar said the study was basically “observational” and conducted in a short time period, which limits the inferences given that it has been common knowledge that more men seem to be affected by Covid than women. 

“They (women) didn’t get infected and those who got infected, less number of them became serious, which essentially means that severity of infection was low.

“Normally when we talk of differences between men and women, that is the first thing anybody will think of (estrogen levels). Otherwise at a particular age, why will more men get affected than women? One of the factors would be the presence of estrogen in the female body, but this is an early observational kind of study. The study has categorically looked at women who are on estrogen and progesterone, which means they haven’t reached menopause. Birth control pills also contain estrogen and progesterone.”

Agreeing, Gujarat-based gynaecologist Dr Soumya Agarwal also said the major “drawback” of the study is that it is “observational” because symptoms are what the patient feels and they will vary from patient to patient. 

“They have also taken only female patients. The study finds post-menupausal patients are more symptomatic, but they haven’t established if it’s only due to the age factor, co-morbidities or estrogen,” she added. 

Dastar also noted that estrogen might be directly responsible for more immunity and less “infectivity” of Covid.

“It could have a multi-factorial origin because we also know in cases of co-morbidities like hypertension and diabetes, the severity and infectivity due to Covid are high. Both these co-morbidities are higher in males than in females, and estrogen is also supposed to be a protective hormone for hypertension,” he added.