Max Casella didn't hit puberty until he was 27.
The 55-year-old actor revealed that he has a "malfunctioning pituitary gland" - which normally regulates growth, metabolism, and reproduction through the hormones that it produces - and "hadn't even shaved" by the time he reached his mid-twenties.
He said: "I have a malfunctioning pituitary gland from birth and basically had to jumpstart my puberty by pumping me full of testosterone and growth hormones to get me to grow because it wasn’t happening. I was 25, and I hadn’t even shaved!"
The 'Doogie Howser, M.D.' star - who has been married to Leona Casella since 2002 and has children Gioia and Mia with her - went on to describe his teenage experience as a "horror show" and likened his inability to speak out to the struggles felt by the transgender community today.
He told The New York Times' PageSix column: "It was a horror show. I couldn’t talk about it. No one understood it. It’s like the trans community today talks about body dysmorphia and feeling like, ‘I’m in the wrong body,’ absolutely my experience. Absolutely. I was a man trapped in a little boy’s body throughout most of my 20s until they finally pumped me full of testosterone."
Meanwhile, Max is now starring opposite Sylvester Stalloen in 'Tulsa King' and felt that it was "surreal" to be working with the 'Rocky' actor after admiring him for so many years.
He said: "I had his poster on my wall when I was 10 years old, and now I’m acting with him? It’s surreal! I've acted with a lot of big stars: Leonardo DiCaprio, Brad Pitt, Johnny Depp. Sometimes it’s up or down, your experience with them, but nobody like Sly, who was such a superhero to my 10-year-old self. This was like my boyhood dream!"