RESUMO
OBJECTIVE: To describe the natural history and estimate the incidence of premature thelarche in girls aged 6 months to 8 years living in Puerto Rico and diagnosed between 1990 and 1995. BACKGROUND: In the 1970s and 1980s, several pediatric endocrinologists, based on their clinical experience, acknowledged a dramatic increase in the number of cases of precocious sexual development in Puerto Rico. In 1987, the Puerto Rico Health Department developed the Registry of Premature Thelarche and Precocious Sexual Development, which began to operate in 1989. Data regarding the long-term outcomes of girls diagnosed with premature thelarche are insufficient. Knowledge about the natural history of this condition is relevant for predicting the long-term prognosis and therapeutic management of the affected population. METHODS: Of 2,716 cases of precocious sexual development reported to the Premature Thelarche and Precocious Sexual Development Registry, 1,916 (70.5) were premature thelarche. The clinical characteristics and evolution during follow-up of premature thelarche cases were described and compared by age group at diagnosis. RESULTS: Incidences were 6.2 and 1.62 per 1,000 live births for girls aged < 2 years and 2 to 8 years, respectively. These estimates were 10 and 15 times higher than those reported in Olmsted, MN. When the average change in mammary tissue diameter during follow-up was evaluated, a slight reduction in girls aged < 2 years was observed; however, it remained constant for girls aged 2 to 8 years. CONCLUSIONS: The results of this study underscore the need to continue an active search of premature thelarche cases and to perform analytical investigations of precocious sexual development to expand the understanding of the etiology of this important public health problem.