RESUMEN
BACKGROUND: The aim of this study was to facilitate the distinction between the benign "mini-puberty of early infancy" and precocious puberty (PP). MATERIAL AND METHODS: We compared 59 patients (21 boys and 38 girls) seen for pubic hair development before one year of age diagnosed as mini-puberty to 13 patients (2 boys) in whom pubertal development before one year revealed a PP. RESULTS: The boys with mini-puberty presented with pubic hair development and prepubertal testicular volume, with low plasma testosterone concentrations. Their gonadotropin responses to gonadotropin releasing hormone (GnRH) test showed predominant luteinising hormone increase in 9/13. The girls presented with pubic hair development that was accompanied by breast development in 47% of cases, with low plasma estradiol concentrations. Their gonadotropin responses showed predominant follicle-stimulating hormone increase in the 17 evaluated. The patients with PP had organic central PP (5 hypothalamic hamartoma) or idiopathic central PP (n=6), or peripheral PP (one ovarian tumor and one congenital adrenal hyperplasia). The diagnosis was challenging only in 3 girls with idiopathic central PP presenting with prepubertal plasma estradiol concentrations and responses to GnRH test. CONCLUSIONS: The diagnosis of PP was easily determined based on the clinical presentation and the pubertal concentrations of testosterone in boys or of estradiol in girls, as was the diagnosis of central or peripheral origin of PP based on gonadotropin response to the GnRH test. Once PP is excluded, these patients need careful follow-up and physician consultation is needed if clinical pubertal signs progress.