Abstract

Context Transient thelarche (TT), that is, the appearance, regression and subsequent reappearance of breast buds, is a frequent phenomenon, but little is known about pubertal transition in these girls. Objective To describe pubertal progression, growth, genotypes, reproductive hormones and growth factors in girls with TT compared to those who do not present TT (non-TT). Design Retrospective analysis of a longitudinal population-based study. Patients or Other Participants Girls (n = 508) of the Chilean Growth and Obesity cohort. Measurements Pubertal progression, reproductive hormones, follicle stimulating hormone (FSH) beta subunit/FSH receptor gene single nucleotide polymorphisms and growth. Results Thirty-seven girls (7.3%) were presented TT. These girls entered puberty by pubarche more frequently (51%) than girls with normal progression (non-TT; n = 471; 23%,P = .005). Girls with TT who were under 8 years old had lower androgens, anti-Mullerian hormone (AMH), luteinizing hormone (LH) and oestradiol (allP < .05) than older girls with TT. At the time of Tanner breast stage 2 (B2), girls with TT had higher androgens, LH, FSH, IGF1, LH, insulin and oestradiol (P < .01) than at the time of TT. TT girls were older at B2 (10.3 +/- 1.1 vs. 9.2 +/- 1.2 years,P < .001) and menarche (12.3 +/- 0.8 vs. 12.0 +/- 1.0 years,P = .040) than their counterparts (non-TT). No differences in anthropometric variables orFSHB/FSHRgenotypes were detected. Conclusion Transient thelarche is a frequent phenomenon that does not appear to be mediated by hypothalamic-pituitary-gonadal axis activation or by adiposity. Hormonal differences between earlier TT and later TT suggest that their mechanisms are different.