Why baldness is linked to coronavirus infection.
Most men hospitalised with COVID-19 are bald according to two small studies. The reason for this is male pattern baldness is associated with high levels of male sex hormones called androgens such as testosterone. Androgens increase the entry of SARS-CoV-2 into cells. Therefore it has been proposed that high levels of androgens may increase the risk of severe infection and death from COVID-19.
Men are more likely to experience more severe infection from COVID-19 than women. Men are more likely to have chronic conditions such as diabetes and heart disease.
Men’s immune system is not as robust as women’s immune system. These factors may be indirectly influenced by sex hormones.
Baldness was more common in patients with COVID-19 admitted to hospital in Madrid, Spain. This study of 122 males showed 79% were bald which is double the population frequency.
Male pattern baldness is strongly associated with higher levels of dihydrotestosterone DHT, the active metabolite of testosterone. It has been proposed that higher levels of DHT could lead to more severe COVID-19 complications.
How does DHT increase the risk of more severe COVID-19 infection?
SARS COVID-19 2 enters human lung cells when a protein on the virus’s surface called the spike protein attaches to a protein receptor, ACE2 receptor on the surface of human cell.
An enzyme called TMPRSS2 cleaves the SARS-COVID-19 2 spike protein allowing it to bind to human ACE2 receptor. This allows the virus to enter the cell.
The gene that encodes TMPRSS2 is activated when DHT bind to the androgen receptor on cells including hair and lung cells.
Therefore if there is more testosterone present, there is more testosterone binding to its receptor and there is more TMPRSS2 present and therefore more virus entering the cell.
Therefore men may be more susceptible to COVID-19 infection and suffer more severely course of disease than women who have lower levels of androgens.
It would be interesting to know if lower levels of androgens in patients are associated with lower risk of COVID-19. Several clinical trials are undergoing trials to determine if androgen reducing drugs reduce complications of COVID-19 in men.
Children under 10 are much less likely to suffer effects of COVID-19 both boys and girls as they produce very little androgens.
To read more of the above article please see The Conversation by Professor Graves https://www.ausdoc.com.au/opinion/why-baldness-linked-coronavirus