Physically precocious young girls often must endure stares and nasty catcalls. The problem of early development is particularly prevalent in Puerto Rico, and researchers there have found a possible culprit.
For more than 2 decades, their island has hosted an inexplicable epidemic of premature breast development, or thelarche. The incidence there—at least 7 or 8 per 1,000 girls—is the highest known. Most of the affected girls begin developing breasts between the ages of 6 and 24 months, notes Carlos J. Bourdony, a pediatric endocrinologist at San Juan City Hospital.