The Russian president has “constantly” been visited by oncology surgeon Yevgeny Selivanov at his Black Sea palace in the past four years.
Mr Selivanov, who specialises in thyroid cancer for “senile patients”, spent 166 days with Putin at his “personal” palace in Sochi.
It has fuelled long-standing rumours that Mr Putin suffers from thyroid cancer.
Those suffering with the disease have a tumour in the neck which often causes a hoarse voice and difficulty swallowing.
Investigative media firm Proyekt says its findings back up theories that Putin launched his Ukraine invasion while suffering from medical problems.
They said his health problems were “the main secret of the Kremlin”.
It comes after footage showing a puffy-faced Putin, 69, sparked rumours he is taking steroids to fight cancer.
Proyekt also found that ear, nose and throat specialist Alexei Shcheglov spent the most time with Putin, visiting 59 times for 282 days.
The report added that he has turned to alternative medicine such as bathing in blood extracted from severed deer antlers.
The unusual practice is rumoured to boost strength and promote youthfulness. However, there is little evidence to corroborate this.
The report by investigative media outlet Proyekt said: “An acquaintance of the president claims that he had been warned that there is no conclusive evidence of the benefits of antler baths. But Mr Putin liked it.”
The Kremlin has repeatedly denied claims about his ill health.
