Height benefit of GnRH agonists after age 8 in a Portuguese cohort of central precocious puberty

Idiopathic central precocious puberty (iCPP) is common in paediatric endocrinology. Gonadotropin-releasing hormone agonists (GnRHa) are safe, but the effect on final height and the ideal timing for treatment remains controversial. This study aims to assess the effectiveness of GnRHa on growth outcomes in girls with iCPP treated before and after the age of 8 years old.This retrospective longitudinal study evaluated data from Portuguese girls with iCPP who completed treatment between 2010 and 2021.Auxological and clinical characteristics were compared according to age at treatment onset.A cohort of 134 girls with iCPP, was divided into early treatment (ET) (<8 years, n = 48) and later treatment (LT) groups (≥8 years, n = 86). In both groups, most children presented with Tanner II and III. Tanner IV was more frequent in LT group (p = .003). At the end of treatment, predicted adult height increased in both groups (ET p = .032; LT p = .04) and bone age significantly slowed down in all participants (p = .008, p = .034). The height gain was greater in the ET group, but without significant differences (p = .065).Treatment with GnRHa improved final height in all girls with iCPP, even when initiated after 8 years. To achieve better outcomes, treatment should be provided promptly after diagnosis.