With his shaved head, lean torso, and broad shoulders, Kevin Larrabee, C.S.C.S., looks like a lot of fitness professionals. At his job at Mike Boyle Strength & Conditioning in Boston, the 30-year-old fits right in with the crowd.

But back when he was a teenager, Larrabee stood out for the wrong reasons. For one thing, he was overweight at 210 pounds. And he had another problem: man boobs.

“I just thought I had the chest of a fat kid,” Larrabee said. So at age 15, he decided to lose the excess poundage.

He ditched the junk food and embraced a healthier, lower-calorie diet. He exercised “a ridiculous amount.”

In three months he dropped to 175 pounds. But somehow he still had those womanly breasts.

Related: 10 Exercises That Will Burn More Calories Than Running

What Larrabee didn’t know was that his condition, gynecomastia—known colloquially as man boobs, mannary glands—was caused by breast tissue, an artifact of the hormonal big bang that hits all boys at puberty.

He also didn’t know that 50 percent of his peers had developed gynecomastia as well but that in most of them it later receded to unnoticeable levels.

“I knew it wasn’t right, but there wasn’t anything I could do about it other than try to lose more weight,” he said. “I was as far as I could get with the knowledge I had.”

Your body is not always a perfect regulator of your hormones, said Dr. Adrian Lo, a plastic surgeon based in Philadelphia who specializes in gynecomastia.

Related: Banish Your Man Boobs With This Workout

In fact, out-of-whack hormones are what cause the formation of excess tissue in the first place: Your testicles produce both estrogen and testosterone, but in early puberty you may not have enough free testosterone (the hormone that builds muscle) to counteract the estrogen. That imbalance allows glandular tissue to form.

“In puberty, many boys have ‘breast buds,’”  Lo explained. “Usually that tissue shrinks to nothing as they grow out of puberty.” For a few, however, it remains. And men can grow breasts in other ways; in fact, as many as 60 percent develop them at some point in their lives.

Some are guys with pubescent gynecomastia that never went away, while others develop man boobs because of medications. Up to 25 percent of gynecomastia cases are caused by meds, according to the journal American Family Physician. 

Some examples: antidepressants, antipsychotics, cholesterol drugs, hair-loss treatments, heartburn remedies, ulcer drugs, ACE inhibitors, and anabolic steroids. 

Related: How to Tell If Someone Is Using Steroids

Then there are the men carrying excess body fat that enlarges their breast tissue, creating the dreaded condition. 

A guy with a bosom born of chest fat instead of tissue has a condition known as pseudogynecomastia. This is the type often seen in overweight men.

Working out or losing weight may help those disappear. (You can lose the extra weight with THE 21-DAY METASHRED. One guy lost 25 pounds in 6 weeks!)

With true gynecomastia, as Kevin Larrabee learned, no amount of exercise or diet vigilance will help.

“Once you have it, you have it,” Lo said. “The only way to take care of it is surgery.”

Lo performs four or five of those procedures a week.

“The men I see are usually pretty fit,” he said. “But most men with gynecomastia qualify for surgery even if they’re not an ideal weight.”

A sliver of breast tissue the size of a silver dollar can be enough to make the areola soft and puffy. Then the man needs to decide whether it bothers him enough to do something about it.

Larrabee was bothered. All through his teen years, he would try to cover up his chest with creatively layered T-shirts and sports jerseys.

Earnings from his part-time jobs were spent on spot-reducing creams and sprays.

“I wasted hundreds of dollars on that stuff,” he said.

In the gym, he built his workouts around chest exercises. He avoided any situation where he might be expected to take off his shirt. But despite his best efforts, people noticed.

Related: Your 5-Step Plan to Living Longer

Finally, in college, Larrabee googled “fat chest” and learned that surgery was his only option. After pleading with his parents to help pay for it, he had the operation in 2007, during his Christmas break.

The first time he saw his new chest was an emotional moment. He compares the experience to looking in the mirror and seeing a different face staring back.

“It was unbelievable,” he said. “I had a flat chest! I couldn’t wait for summer.”

Like cosmetic breast implants, gynecomastia surgery is rarely covered by insurance. It costs anywhere from $5,000 to $8,000. But for Larrabee, it was a bargain.

“At the end of the day,” he said, “it was a miracle that worked.”

This article originally appeared on MensHealth.com.