"He passed away from a sudden death at his home in Coral Gables," publicist Susan Biegacz of Tractenberg & Co. told People.
Meanwhile, Brandt's publicist, Jacquie Tractenberg, told the New York Post's Page Six that he died after "suffering from an illness."
The doctor's celebrity patients included Madonna, Kelly Ripa and model Stephanie Seymour.
Dr. Brandt admitted that he did use his own face to test out products and procedures. "I've been kind of a pioneer in pushing the limits to see how things work and what the look would be," he told The New York Times last March. "Would I change anything I've done? I might not have used as much Botox, because you don’t want to look quite as frozen."
As for his patients, "I want people to feel they haven't given up on life and are still in the game," he explained his vision.
"If I have nice skin, I owe a lot to him," Madonna told the Times in an email.
In addition to his thriving practices in both Manhattan and Coral Gables, Fla., Dr. Brandt also hosted a weekly radio show on Sirius XM and had a skincare line.
According to a Miami Herald blogger, Dr. Brandt had suffered from a bout of depression after becoming "devastated" by comparisons to Martin Short's plastic surgeon character in Netflix's Unbreakable Kimmy Schmidt.