In a recent interview, singer Rod Stewart told Mojo magazine that the corticosteroids he used to soothe inflammation in his vocal cords had a couple of nasty side effects - most notably, the singer admitted, the shrinking of his penis.

"I let myself down on tours in the late 80s when I was addicted to steroids. In those days we didn't have in-ear monitors and the band kept getting louder and drunker, and I kept blowing my voice out," 68-year-old Stewart told Mojo, as reported by the New York Daily News. "The steroids will take down the swelling in any membrane - including your knob - and it's what you do when you're in a bit of a pinch and need to do a show and you can't sing."

The "Da Ya Think I'm Sexy?" singer called steroids "one of the most horrible drugs in the world," adding that they made him fat, bloated, irritable, and unable to sleep, according to Digital Spy. After prolonged use, he said, the drugs ate a hole through his stomach and caused internal bleeding.

Despite the side effects, though, Stewart said he still uses steroids on occasion, "if [he's] really struggling," the Daily News reports. "It gets you through the show," he added.

Corticosteroids, which are different from the anabolic steroids some athletes take, are meant to mimic the effects of the hormone cortisol, which is produced naturally by the adrenal glands, the Cleveland Clinic says. They work by decreasing inflammation and mitigating the activity of the immune system, making them effective for treating problems like rheumatoid arthritis, asthma, or certain other conditions where the immune system is working against the body or inflammation.

"When inflammation threatens to damage critical body organs, steroids can be organ-saving and in many instances, life-saving," the Cleveland Clinic says. "For example, steroids may prevent the progression of kidney inflammation, which could lead to kidney failure in people who have lupus or vasculitis. For these patients, steroid therapy might eliminate the need for kidney dialysis or transplantation."

But there are also side effects to these medications, which is why doctors generally take care to follow certain guidelines in prescribing them, the Clinic adds. Overuse of corticosteroids can lead to weight gain, mood swings, swollen face, water retention, stomach irritation, and even osteoporosis and insomnia. The drugs could even lead to a shrinking of the soft tissues, says the Mayo Clinic, which could explain Stewart's genital shrinkage.

Brevity of steroid use will likely mean a patient won't experience these side effects, the Cleveland Clinic adds. But prolonged use and high doses could increase the number and severity of the side effects. "The prolonged use of high dose steroids is justified only for severe illnesses that represent serious risks to the patient."