Com o objetivo de estabelecer o valor de corte e distinguir telarca precoce isolada (TPI) de puberdade precoce (PP), avaliamos 79 meninas com telarca precoce, comparando as dosagens basais e pós-estímulo de LH e FSH com grupo-controle. O teste de estímulo com GnRH foi realizado em 10 meninas normais e em 42 com telarca precoce. Os testes de Kruskal-Wallis and Dunn foram usados na comparação dos grupos. Os níveis de LH foram significativamente mais elevados no grupo com TPI, quando comparados com controles. As gonadotrofinas basais foram mais elevadas naquelas com PP que nos controles, mas não diferiram do grupo com TPI. O pico de LH após GnRH distinguiu estes dois grupos, com valor de corte de 4,0 UI/L, apesar de pequena sobreposição. Concluímos que uma menina com telarca precoce e LH pós-estímulo acima de 4,5 UI/L apresenta PP, mas valores entre 3,5 e 4,5 UI/L requerem seguimento cuidadoso.

In order to establish cut-off limits and to distinguish isolated premature thelarche (IPT) from precocious puberty (PP), we evaluated data from 79 girls with premature thelarche, comparing basal and stimulated LH and FSH serum concentrations with those from 91 healthy girls. A GnRH stimulation test was performed in 10 normal girls and in 42 with premature thelarche. Comparison among groups was performed by Kruskal-Wallis and Dunn’s tests. LH values were significantly greater in girls with IPT than in control groups. Basal gonadotropin concentrations were higher in patients with PP than in controls, but not different from patients with IPT. Peak LH levels after GnRH stimulation distinguished those two groups, with a cut-off value of 4.0 IU/L, but still with minimal overlap. In conclusion, a girl with premature thelarche and LH peak value above 4.5 IU/L has, indeed, PP, but values between 3.5 and 4.5 IU/L point to careful follow-up.