Puberty Before Age 10: A New ‘Normal’?
For many parents of early-developing girls, “normal” is a crazy-making word, especially when uttered by a doctor; it implies that the patient, or patient’s mother, should quit being neurotic and accept that not much can be done. Allomong listened intently. He nodded and took notes, asking Tracee detailed questions about her birth-control history and validating her worst fears by mentioning the “extremely high levels” of estrogen-mimicking chemicals in the food and water supply. After about 20 minutes he asked Ainsley to lie on a table. There he performed a lengthy physical exam that involved testing the strength in Ainsley’s arms and legs while she held small glass vials filled with compounds like cortisol, estrogen and sugar. (Kinesiologists believe that weak muscles indicate illness, and that a patient’s muscles will test as weaker when he or she is holding a substance that contributes to health problems.)
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Now most researchers seem to agree on one thing: Breast budding in girls is starting earlier. The debate has shifted to what this means. Puberty, in girls, involves three events: the growth of breasts, the growth of pubic hair and a first period. Typically the changes unfold in that order, and the process takes about two years. But the data show a confounding pattern. While studies have shown that the average age of breast budding has fallen significantly since the 1970s, the average age of first period, or menarche, has remained fairly constant, dropping to only 12.5 from 12.8 years. Why would puberty be starting earlier yet ending more or less at the same time?
To endocrinologists, girls who go through puberty early fall into two camps: girls with diagnosable disorders like central precocious puberty, and girls who simply develop on the early side of the normal curve. But the line between the groups is blurring. “There used to be a discrete gap between normal and abnormal, and there isn’t anymore,” Louise Greenspan, a pediatric endocrinologist and co-author of the August 2010 Pediatrics paper, told me one morning in her office at Kaiser Permanente in San Francisco. Among the few tools available to help distinguish between so-called “normal” and “precocious” puberty are bone-age X-rays. To illustrate how they work, Greenspan pulled out a beautiful old book, Greulich and Pyle’s “Radiographic Atlas of Skeletal Development of the Hand and Wrist,” a standard text for pediatric endocrinologists. Each page showed an X-ray of a hand illustrating “bone age.” The smallest hand was from a newborn baby, the oldest from an adult female. “When a baby is born, there’s all this cartilage,” Greenspan said, pointing to large black gaps surrounding an array of delicate white bones. As the body grows, the pattern of black and white changes. The white bones lengthen, and the black interstices between them, some of which is cartilage, shrink. This process stops at the end of puberty, when the growth plates fuse.
full: http://www.nytimes.com/2012/04/01/magazine/puberty-before-age-10-a-new-normal.html?pagewanted=all
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