Dear Editor
In late 2019, a novel coronavirus, subsequently named SARS‐CoV‐2 (COVID‐19), was first
reported in Hubei province in China. Since it was first reported, a worldwide pandemic
has ensued affecting more than 450 000 individuals as of March 2020. In the midst
of the pandemic, epidemiological reports unveiled a disproportionate low rate of severe
cases among adult females compared to adult males, 42% and 58%, respectively.
1
Similarly, the rate of severe cases among pre‐pubescent children was exceptionally
low at 0.6%.
1
An explanation for the skewed prevalence of severe COVID‐19 infection in adult males
has yet to be elucidated.
In newborns, it has long been recognized that male infants are more susceptible to
respiratory distress syndrome
2
and less likely to respond to prenatal glucocorticoid therapy to protect against respiratory
distress.
3
Respiratory distress is intimately tied to the production of pulmonary surfactant,
for example, pulmonary surfactant proteins have been demonstrated to protect against
influenza A.
4
In animal studies, it was demonstrated that a sexual dimorphism in fetal pulmonary
surfactant production is influenced by the androgen receptor (AR).
5
For example, in rabbits, dihydrotestosterone was shown to inhibit fetal pulmonary
surfactant production in both males and females while an anti‐androgen, flutamide,
was demonstrated to remove the sexual dimorphism in surfactant production.
3
While severe COVID‐19 symptoms are primarily manifested in older adults, the similar
sexual dimorphism in the severity of respiratory disease is of interest. In addition,
AR expression is low prior to pubertal maturation and may contribute to the low incidence
of severe COVID‐19 infection in children.6, 7, 8 As such, we propose that the lower
rate of severe COVID‐19 infection in female patients may be attributed to lower AR
expression.9, 10
Additional evidence to the possible implication of androgens in COVID‐19 infection
severity is found in the molecular mechanism required for SARS‐CoV‐2 infectivity.
SARS‐CoV‐2 is part of the coronavirus family of viruses including SARS‐CoV‐1 and MERS‐CoV.
Coronavirus predominantly infects type II pneumocytes in the human lung.
11
Previously, it was demonstrated that SARS‐CoV‐2 cell entry depends on priming of a
viral spike surface protein by transmembrane protease serine 2 (TMPRSS2) present in
the host.12, 13 In type II pneumocytes, TMPRSS2 expression is associated with an increase
in AR expression,
14
specifically connecting AR expression to SARS‐CoV‐2, due to AR‐regulated TMPRSS2 gene
promoter (Figure 1).
15
Moreover, angiotensin‐converting enzyme 2 (ACE2) has been recognized as the attachment
molecule to the viral spike surface protein, thus termed the “receptor of SARS‐CoV‐2”.
16
Interestingly, ACE2 has been shown to have reduced activity by the decrease of androgen
hormones (experimental orchidectomy), possibly by decreased expression of ACE2.
17
FIGURE 1
TMPRSS2 gene transcription promoter site requires an activated androgen receptor,
with androgens such as testosterone. Dihydrotestosterone (DHT) a potent androgen receptor
activator and is intracellularly produced in particular cells of tissues such as prostate,
hair, and liver that express 5‐alpha‐reductases, the targeted enzyme for drugs such
as dutasteride and finasteride (5‐alpha‐reductase inhibitors)
To test this hypothesis, it would be informative to study the epidemiology of COVID‐19
patients that are predisposed to either lower or higher AR expression, such as, males
suffering from androgenetic alopecia, benign prostatic hyperplasia, or women suffering
from polycystic ovary syndrome. In addition, analyzing ethnic variation in AR expression
may predict COVID‐19 ethnic mortality differences. Additionally, the activation of
AR can be reduced by several classes of drugs including AR antagonists, androgen synthesis
inhibitors, and antigonadotropins. For example, the FDA‐approved 5‐alpha reductase
inhibitor finasteride demonstrated reduction of activation of AR in multiple tissues.
10
Other potential drugs that could be studied include: cyproterone acetate, megestrol
acetate, chlormadinone acetate, spironolactone, medrogestone, oxendolone, osaterone,
bifluranol acetate, flutamide, bicalutamide, nilutamide, topilutamide, enzalutamide,
apalutamide, dienogest, drospirenone, medrogestone, nomegestrol acetate, promegestone,
trimegestone, ketoconazole, abiraterone acetate, seviteronel, aminoglutethimide, dutasteride,
epristeride, alfaestradiol, and isotretinoin. Taken together, the evidence warrants
further studies to elucidate the role (if any) of the AR on the severity of COVID‐19
infection.
CONFLICT OF INTEREST
The authors declare no potential conflict of interest.