The real reason for Elvis Presley 's death has been a mystery for years as the circumstances behind The King's demise have been a closely guarded secret.
His family sealed the autopsy results for 50 years after the original rock and roll star - who would now be 89 - died at his Graceland home on August 16, 1977 aged just 42, much to the shock and utter disbelief of his fans.
Just four years from now, that time will be up and the mysterious questions surrounding The King's passing will finally be answered. Although in the years since, many have shared their theories.
Tragically, Elvis had spent the last decade of his life in ill-health after years of drug abuse.
In the run-up to his death, the once-lithe Hound Dog star weighed 25 stone and had spent months gorging on cheeseburgers in his room, which he refused to come out of.
According to reports, he needed a full-time nurse and apparently refused to bathe throughout 1975, causing him to develop sores on his body.
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As a result of his horrendous diet, he suffered from chronic constipation and a post mortem found he had compacted stool that was four months old sitting in his bowel.
The singer was also on a cocktail of drugs and had been prescribed almost 9,000 pills, vials and injections in the seven months before his death.
An autopsy was carried out but the report was immediately sealed for 50 years by the family, sparking a slew of speculation as to what killed him.
Dan Warlick, chief investigator for the Tennessee Office of the State Chief Medical Examiner, attended the autopsy and fuelled the popular theory that Elvis died while straining to go to the toilet.
He once said: "Presley's chronic constipation - the result of years of prescription drug abuse and high-fat, high-cholesterol gorging - brought on what's known as Valsalva's maneuver. Put simply, the strain of attempting to defecate compressed the singer's abdominal aorta, shutting down his heart."
Others claimed he'd died from a drug overdose, but when the investigation was reopened in 1994, coroner Joseph Davis disagreed.
He explained: "The position of Elvis Presley's body was such that he was about to sit down on the commode when the seizure occurred. He pitched forward onto the carpet, his rear in the air, and was dead by the time he hit the floor.
"If it had been a drug overdose, [Elvis] would have slipped into an increasing state of slumber. He would have pulled up his pajama bottoms and crawled to the door to seek help. It takes hours to die from drugs."
The autopsy results are due to be unlocked in 2027, but until then, the biggest insight into the star's mysterious death has come from prominent California physician, Forest Tennant, who actually reviewed the report while defending Elvis' doctor, Dr. George Nichopoulos, who was later acquitted of over-prescribing drugs.
For Mr Tennant, one major clue was in the full-body deterioration of Elvis, with almost every organ plagued by ill health.
As a young man Elvis had been extremely fit, playing football and practicing martial arts. He did start abusing drugs including amphetamines, opioids and sedatives as a teenager and is known to have had an appalling diet.
But for Tennant, that wasn't enough to explain the long list of maladies that afflicted the rock star from the late 1960s onwards.
First he complained of vertigo, back pain, and insomnia, eye infections and headaches, and in 1973 he was rushed to hospital in a semi-coma and found to be suffering from jaundice, severe respiratory distress, marked swelling of his face, distended abdomen, constipation, a gastric, bleeding ulcer and hepatitis.
He was hospitalised again in 1975 with high blood pressure, high cholesterol and a condition called megacolon, whereby the large intestine becomes distended and can allow toxins to flood the body.
He also had at least four near-death overdoses that left him unconscious and in need of resuscitation, and his heart was double the normal size.
And despite having never smoked, he also suffered from emphysema. So what had caused all of these disease processes in his stomach, liver, lungs, heart, spine, eyes and bowel?
Forest believes it all stemmed back to a serious head injury he sustained in 1967 that triggered a progressive autoimmune inflammatory disorder.
In his opinion, as shared in a 2013 medical paper, when Elvis tripped over a television cord and knocked himself out on the bathtub, the injury was so severe that it caused brain tissue to dislodge and seep into his blood circulation.
There, the body identified the matter as foreign and produced antibodies to destroy it, triggering hypogammaglobulinemia, a disorder of the body's immune system.
At the time, little was understood about auto-immune conditions, but these days they are known to cause most of the symptoms Elvis displayed, from chronic pain, irrational behaviour, obesity and enlarged and diseased organs like hearts and bowels.
And in 2016 Garry Rodgers, a retired homicide detective and forensic coroner, told the Huffington Post that with those findings in mind, he would have attributed Elvis' death to a heart attack caused by heart disease and drug use caused by an autoimmune disease which was sparked by a brain injury.
He said: "I'd have to classify Elvis' death as an accident. There's no one to blame - certainly not Elvis. He was a severely injured and ill man.
"There's no specific negligence on anyone's part and definitely no cover-up or conspiracy of a criminal act.
"If Dr. Forrest Torrent is right, there simply wasn't a proper understanding back then in determining what really killed the King of Rock and Roll."
It was his girlfriend Ginger Alden who found the rock and roll star's body with his pyjama bottoms around his ankles and his bottom in the air.
Of the distressing scene, Ginger, who was just 21 at the time, wrote in her memoir: "His arms lay on the ground, close to his sides, palms facing upward.
"It was clear that, from the moment he landed on the floor, Elvis hadn't moved."
She continued: "I gently turned his face toward me. A hint of air expelled from his nose.
"The tip of his tongue was clenched between his teeth and his face was blotchy.
"I gently raised one eyelid. His eye was staring straight ahead and blood red."
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