Though still preliminary and not peer reviewed, the study is the first clinical observation of the potential impact of Covid-19, the disease caused by the coronavirus, on the male reproductive system, especially among younger groups.

In a paper published on the preprint research platform  medRxiv.org, the researchers – from Zhongnan Hospital of Wuhan University and the Hubei Clinical Research Centre for Prenatal Diagnosis and Birth Health – said they analysed blood samples from 81 men aged 20 to 54 who tested positive for the coronavirus and were hospitalised in January.

The median age of the participants was 38 and roughly 90 per cent of them had only mild symptoms. The samples were collected in the last days of their stay in hospital. -SCMP

Previous studies have shown that coronavirus binds with the protein receptor cell, ACE2, a large number of which are found in the testicles.

Researchers looked at the ratio of testosterone to luteinising hormone (T/LH) - finding that the average ratio for COVID-19 patients was 0.74, around half the normal level. A low T/LH ratio can signal hypogonadism - a malfunction of the testicles which could lead to lower production of the sex hormone.