Premature thelarche in Puerto Rico. A search for environmental factors.

Pediatric endocrinologists in Puerto Rico reported a threefold increase in the number of patients with premature thelarche seen between 1978 and 1981. A matched-pairs case-control study was conducted to evaluate associations with potential environmental exposures to substances with estrogenic activity, as well as with familial factors. Analysis was performed on 120 pairs, the case subjects of which were selected from those diagnosed between 1978 and 1982. In subjects 2 years of age or older at the onset of thelarche, no significant associations were found. In subjects with onset before 2 years of age, significant positive associations were found with a maternal history of ovarian cysts, consumption of soy-based formula, and consumption of various meat products. A statistically significant negative association was found with consumption of corn products. These statistical associations are probably not sufficient to explain the reported increase because in over 50% of the case subjects there was no exposure to any of the risk factors for which statistical associations were found. Exposure to other substances with possible estrogenic effect, such as waste products from pharmaceutical factories and pesticides, was also excluded as a possible cause. These findings suggest that better diagnosis and reporting, or conceivably the presence of entirely new, unsuspected factors, could account for the reported increase.