The media have portrayed the scenario hundreds of times: a male character on television or in a movie receives an injury below the belt and his voice suddenly rises. The situation may provide audiences with slapstick entertainment, but does this ever happen in real life? In a word, no. You are witnessing what amounts to a special effect. The truth about how voice develops over time makes it clear why this scene perpetuates a medical myth.
Just as the shortest strings on a harp or piano make the highest sounds, the short vocal cords of children produce voices that are high in pitch. As we age, especially during puberty, our vocal cords lengthen and increase in thickness, in part because of overall growth but also in response to hormones circulating in higher amounts. For boys, the change during puberty is often dramatic because increased production of testosterone (most of which is secreted by the testicles) increases the length of vocal cords more than 60%. Sometimes the change seems abrupt — over only a few weeks or months, the voice begins to crack and then becomes deeper and more resonant. Once the change occurs, there's typically no going back. Meanwhile, girls' vocal cords, now under the influence of female hormones, lengthen a more modest 25% during puberty.
So why is there a misconception about the ability of the voice to change suddenly with an injury? It probably relates, at least in part, to the real connection between male hormones produced by the testicles and the role of these hormones in lowering boys' voices. But the flaw lies in believing that the process is promptly reversible.
As painful as such an injury might be and whatever other pain reactions a person might have, it would not be expected to suddenly change hormone levels. Even if it did, vocal cords that have increased in size in response to testosterone do not change much in their length or mass once puberty has passed. For example, adult men who develop diminished testosterone production in adulthood do not develop particularly high voices.
It is true that if a boy does not go through puberty because of deficient testosterone, his voice remains high. In fact, in the 16th, 17th and 18th centuries, boys ages 7 to 9 in Italy with a talent for singing operatic or religious music were sometimes castrated to preserve the high pitch into adulthood. If adult women take male hormones (for example, as a medical treatment), their voices will become irreversibly lower in pitch.
So when the kid in "Home Alone" gets his revenge on the bad guys, realize that although the injured party sounds like Tweety Bird, it's just a medical myth perpetuated in the name of entertainment.
Robert H. Shmerling, M.D. is associate physician at Beth Israel Deaconess Medical Center and associate professor at Harvard Medical School. He has been a practicing rheumatologist for over 20 years at Beth Israel Deaconess Medical Center. He is an active teacher in the Internal Medicine Residency Program, serving as the Robinson Firm Chief. He is also a teacher in the Rheumatology Fellowship Program.