Premature thelarche: a long-term follow-up.

The differentiation between premature thelarche and idiopathic central precocious puberty is essential for both long-term prognosis and therapeutic approach but, until now, there have been insufficient data to predict the future of the girls with premature thelarche. We studied 46 girls with premature thelarche longitudinally. The girls were subdivided into two groups according to the time of onset of thelarche: Group A consisted of 26 girls who presented thelarche before the second year of life (mean +/- SD 14.7 +/- 5.2 months) and Group B contained 20 girls who showed breast enlargement after the second year of life (5.7 +/- 3.1 years). The mean basal follicle-stimulating hormone (FSH) level of the patients as a whole was significantly higher than normal values (2.1 +/- 0.05 vs. 0.7 +/- 0.9 mIU/ml, p < 0.01) and the luteinizing hormone (LH) level was not significantly different from that in healthy control subjects (0.8 +/- 0.6 vs. 0.6 +/- 0.7 mIU/ml). After gonadotropin-releasing hormone test the FSH response was significantly higher than normal prepubertal values (12.9 +/- 2.1 vs. 3.9 +/- 2.9 mIU/ml, p < 0.001) whereas the LH response did not differ significantly (1.8 +/- 0.6 vs. 1.7 +/- 0.9 mIU/ml). After a follow-up time ranging from 5.1 to 7.8 years (mean +/- SD 5.9 +/- 1.9) we observed a greater percentage of disappearance in the girls in Group A than in those in Group B. The present data show that the percentage of girls who developed precocious puberty was significantly higher when they presented thelarche after the age of 2 years than before; the age of onset of thelarche can be useful to distinguish patients at risk of progressing towards precocious puberty.