Garry Shandling's cause of death is still unknown.
Although the late comedian's publicist, Alan Nierob, told ET on Friday that doctors believe Shandling died as a result of a heart attack
, the Los Angeles Coroner's Office confirms to ET that his doctor refused to sign his death certificate.
"This was not Garry's primary physician," Assistant Chief Coroner Ed Winter explains to ET. "He has only known Garry a couple years, but he did not see him regularly."
The Coroner's Office has now taken custody of the case, and an examination was performed, although Shandling's cause of death has been deferred pending toxicology and other tests. Winter tells ET that there were some other medical issues at hand, but would not divulge as to what they were.
Shandling died on March 24
at the age of 66. He had no history of heart problems, Nierob told ET. But, during his recent appearance on Jerry Seinfeld's Crackle show, Comedians in Cars Getting Coffee
-- titled "It's Great That Garry Shandling Is Still Alive" -- he did talk about having an undiagnosed health ailment.
"So it turns out I had a hyper parathyroid gland that was undiagnosed because the symptoms mirror the exact same symptoms an older Jewish man would have, which is, you know -- lethargic, you get puffy, you get heavy, you kind of feel like you want a divorce, but, you know, you’re not married," he joked during the episode, which aired in January.
Common complications of hyperparathyroidism -- caused by too little calcium in the bones and too much calcium circulating in the bloodstream -- include osteoporosis, kidney stones, high blood pressure, and certain types of heart disease.
The Larry Sanders Show
star experienced shortness of breath and pain in his legs just a day before his death, People
reports. Shandling spoke to a doctor friend about his symptoms, who stopped by that night to check on him, and when he still wasn't feeling well the next day, Shandling told his friend he was going to go to the hospital. He died the very same day.
The Coroner's Office confirms to ET that they did speak to the doctor in question during their investigation, but did not subpoena any medical records because he was not the primary care physician. The Coroner's Office has already reached out to Shandling's primary care doctor to request his medical history, but have been unable to obtain any medical records because Shandling has not seen the doctor in over a year.
The iconic comedian's death has been a shock to Hollywood, and plenty of his famous friends have paid tribute to Shandling
, including Kathy Griffin, Ricky Gervais, Steve Martin, Billy Crystal, and Ellen DeGeneres.