Can Steroids Enlarge Your Head?

What a change in hat size might mean for Barry Bonds.

Barry Bonds

Following the federal indictment of Barry Bonds for perjury and obstruction of justice last week, media reports cited the baseball player’s refusal to “admit that steroids contributed to his swollen head and bloated physique,” and drew a line from his alleged use of performance-enhancing drugs to his “noticeably bigger” skull. Can doping really make your head get bigger?

Yes, but steroids can’t. Although much of Bonds’ testimony dealt with anabolic steroids, he is also charged with having lied about taking human growth hormones. And HGH can indeed affect the size of your noggin. The hormone, which is produced by the pituitary gland, normally stimulates bone and tissue growth throughout the body. If there’s too much of it, the body starts to develop an abnormal amount of flesh and bone. This affects the entire body to some degree, but in some places the chemical receptors tend to be especially sensitive. In an adult, very large doses of HGH can cause the skull to thicken and the forehead and eyebrow ridge to become especially prominent. Hands and feet also grow out of proportion with the rest of the body.

Almost all adults with this condition, called acromegaly, have a tumor in the pituitary gland, and the changes happen so gradually that they might only notice after looking at themselves in an old photograph. If a patient is young enough that his or her bones are still growing, exposure to all that HGH will result in gigantism, the condition that Andre the Giant is believed to have had. But adults that develop acromegaly get thicker, not taller, with the most striking changes usually in the head, hands, and feet.(One book about Bonds claimed that his hat size grew from 7⅛ to 7½, a difference of about an inch in circumference, and that his shoe size shot from 10½ to 13. Bonds has countered that nothing’s changed, saying in one interview, “My head hasn’t grown. I’ve always been a 7¼ to a 7⅜ my whole career.“)

What about anabolic steroids? They don’t give you a big head, but they might make you a bit more like a woman—a bald woman. The body converts a portion of anabolic steroids, which are synthetic forms of testosterone, into estrogen, which causes breast enlargement. Researchers also believe that huge doses of testosterone can cause testicles to shrink by one-quarter or one-third of their original size. And anabolic steroids, like testosterone, can cause hair loss.

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Explainer thanks Linn Goldberg of Oregon Health Sciences University, Norm Mazer of Boston University, and Gary Wadler of the World Anti-Doping Agency.