Vladimir Putin has been accused of taking steroids that make users more aggressive.
Former foreign secretary Lord David Owen said he suspects steroid use due to changes in the shape of Putin's face, which could be caused by muscle-boosting drugs.
Lord Owen told Times Radio: "Look at his face, see how that has changed - he now has an oval face.
"People who said, oh, it's plastic surgery or Botox, I don't believe that at all.
"He's on either anabolic steroids as a bodybuilder - and he's very proud of his muscles and strips to the waist and everything like that - or he's on corticosteroids.
"If you're on these drugs, this gives you this face.
"It reduces your immunity and makes you more vulnerable to Covid.
"This man has been in complete isolation, quite extraordinary, won't see anybody, stays miles away, tremendous pressures.
"Which indicates he's on a steroid and probably, maybe, a combination of both."
Lord Owen said the anabolic steroids can increase a person's aggression.
It comes after experts fear the Covid-19 pandemic scrambled Vladimir Putin ’s mental health, sparking the paranoia which led to the invasion of Ukraine.
The Russian president had limited contact with people during the worst of the events of the last two years, with those in his very inner circle having to isolate before being granted an audience.
Putin’s insistence he ordered troops into his peaceful neighbour's territory to protect people subjected to bullying and genocide- of which there is no evidence- has fuelled fears for his mental health.
He also said his troops are there for the demilitarisation and de-Nazification" of Ukraine, claims which have been met with astonishment by the leaders of the under siege nation.
Some insist Putin is still feeling the effects of “brain fog”, as a result of long Covid.
Other examples pointing to potential causes of alarm in the Kremlin leader, 69, include rumours he has been practically a recluse since the start of the pandemic.
Such are his concerns of the virus he insists meetings are held via video link - or across ludicrously long tables, insisting each participant sits at either end.
His inner circle are also forced to provide stool sample several times a week so Putin is not infected.
Marco Rubio, the Republican Senator for Florida, tweeted: “I wish I could share more, but for now I can say it’s pretty obvious to many that something is off with Putin.
“He has always been a killer, but his problem now is different & significant.
“It would be a mistake to assume this Putin would react the same way he would have five years ago.
“Putin’s inner circle went along with a #UkraineInvasion plan they knew was unrealistic & could lead to a quagmire.
“Soon they may have to decide whether to go along with new orders that will make them internationally wanted war criminals for the rest of their lives.”
“This is a very dangerous moment.”
