Santino Fontana is at war with his bra. Also his heels. Also the sausage-casing underwear intent on smushing his body into a smaller, sleeker, backfat/bump/wobble/jiggle-free hourglass version of itself that nature surely never intended.

In other words, the 36-year-old star of the Broadway-bound musical “Tootsie,” which begins performances Tuesday in Chicago at the Cadillac Palace Theatre, is learning a hard truth: The physics of foundation garments make the physics of string theory look like kindergarten.

“I was completely unaware [of what] so many women deal with,” Fontana says. “So much elastic. And straps. And boning.”

Don’t even get him started on heels. He’s been trying “to get a leg up” on the kind of posture-defying shoes engineered to make forward and backward-thrusting shelves of (respectively) one’s bazooms and behind.

When: Tuesday-Oct. 13
Where: Cadillac Palace Theatre, 151 W. Randolph
Tickets: $35-$105, plus premium packages

So it goes as Fontana struggles to master the dual-gender role of Michael Dorsey/Dorothy Michaels. Like the title character played by Dustin Hoffman in the 1982 movie “Tootsie,” Michael in the musical “Tootsie” is a struggling actor who finds stardom after donning a dress and sallying forth as Dorothy.

“It feels like there’s a pit crew following me around dealing with hair, makeup and clothes. It takes a village,” says Fontana, who is perhaps best known for playing Greg, the alcoholic king of sarcasm in Rachel Bloom’s subversive musical sitcom “Crazy Ex-Girlfriend.”

There is indeed a village of talent working to bring “Tootsie” to the stage, including director Scott Ellis, book writer Robert Horn, lyricist-composer David Yazbek and choreographer Denis Jones.

Opening in previews Tuesday at the Cadillac Palace, the musical — slated for a spring debut on Broadway — follows the same general plot as the movie released nine months before Fontana was born: In pants, Michael is an unemployed actor. In a dress, he’s a gale-force superstar feminist.

Padding and general plot aside, musical “Tootsie” veers sharply from movie “Tootsie.”

Michael Horn, wrote the book for the “Tootsie” musical, based on the 1982 movie.

Robert Horn, wrote the book for the “Tootsie” musical, based on the 1982 movie. | Colin Boyle / Sun-Times

“Obviously, the politics are way different today than they were in 1982,” Horn says. “The role of women in our culture has changed, as has the role of men. It’s been exciting to update this, to reflect those changes.”

Those updates will be obvious from the opening number. “Tootsie” the musical is set in the present day, not in the 1982 era of shoulder pads and sculpturally massive hair. Playing to Fontana’s strengths, the gig Michael-as-Dorothy lands isn’t on a soap opera as in the movie, it’s in a musical.

There’s general agreement among Horn and cast members that Michael Dorsey starts out as a jerk. This is, after all, a man who has no problem lying and taking a lucrative role that might have gone to (among other actual women) his best friend.

“Michael’s decision to pretend to be a woman is terrible,” Fontana says. “Like many people, he makes an impulsive decision and realizes the consequences of his actions after the fact. And we definitely deal with that.”

Says Horn: “Michael has a massive ego. He’s arrogant. You might not like him initially. But you’ll understand him because everyone understands desperation. How far are you willing to go to get that one thing you want more than anything?

“Michael is desperate. He’ll go pretty far.“

The role of actress Julie Nichols — played in the movie by Jessica Lange and on stage by Lilli Cooper — is among those unwittingly caught up in Michael’s deception. In the movie, Julie is stuck in an abusive relationship with Ron, a piggish director. There’s no such relationship in the musical “Tootsie.”

As his alter ego Dorothy befriends soap opera co-star Julie Nichols (Jessica Lange, left), actor Michael Dorsey (Dustin Hoffman) falls in love with her in the movie "Tootsie."

As his alter ego Dorothy befriends soap opera co-star Julie Nichols (Jessica Lange, left), actor Michael Dorsey (Dustin Hoffman) falls in love with her in the movie “Tootsie.” | Columbia Pictures

“Ron’s definitely interested in Julie, but she’s able to sort of use that to her advantage,” Cooper says. “She understands that weak and vulnerable men like Ron are — how can I describe this? — malleable. She’s not manipulative, but she knows how to use that in a way that will mean more shows and more jobs down the line.”

For all its glitter and romance (Fontana’s role as Prince Topher in Broadway’s 2013 “Cinderella” is pure, rosegold fairytale), musical theater isn’t all dreamy ballgowns and shiny tiaras. That, too, is evident in “Tootsie” the musical.

“We’re getting into the neurosis and the struggle of it,” Horn says. “Like, when you’re living with five roommates and eating ramen three times a day because that’s what you have to do to follow your dream.”

Fontana is beyond that stage. He’s been working steadily on Broadway for a decade and snagged a Tony nomination for his Prince Topher. But he has this to say for the Michael Dorseys living on ramen and desperation.

“You gotta follow what you get the most enjoyment out of doing. Because eventually that’s all you’re in control of. I try to remind students when I talk to them that Broadway isn’t a destination, it’s a street.”