Worldwide Secular Trends in Age at Pubertal Onset Assessed by Breast Development Among Girls: A Systematic Review and Meta-analysis

Reproductive hormones during pubertal transition in girls with transient Thelarche

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-Müllerian hormone (AMH), luteinizing hormone (LH) and oestradiol (all P < .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 or FSHB/FSHR genotypes 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.

Connections Between Obesity and Puberty: Invited by Manuel Tena-Sempere, Cordoba

The relationship between obesity and puberty remains controversial. Whereas cross-sectional and longitudinal studies show a clear shift toward earlier puberty in obese girls, the trend in obese boys remains less obvious. Overweight boys mature earlier whereas obese boys mature later compared to healthy weight boys. Newer epidemiologic studies attempt to address these knowledge gaps. This review provides a detailed overview of the recent literature regarding secular trends in pubertal onset and tempo, and the connection with obesity. Additionally, this review summarizes potential mediators that permit obesity to promote early puberty. Other factors such as socioeconomic status, in utero exposures, nutritional, and even endocrine disrupting chemicals can cause perturbation of both metabolism and the endocrine axis that can ultimately have effects on pubertal development.

How can two biological variables have opposing secular trends, yet be positively related? A demonstration using timing of puberty and adult height

Timing of puberty and adult height have opposing secular trends yet are positively associated in individuals. We demonstrate this using data from a single sample and discuss possible statistical and epidemiological reasons behind it. The sample comprised 365 females from Fels Longitudinal Study born 1929-1992. We used Super-Imposition by Translation and Rotation (SITAR) to estimate individual age at peak height velocity (PHV) and PHV from serial height data (8149 observations between 5 and 24 years). General linear regression was used to investigate the association between height and age at PHV, and secular trends in height, age at PHV and PHV. Although adult height increased 0.42 (95% CI: 0.08, 0.77) cm per decade, and age at PHV decreased 1.14 (-3.74, 1.45) weeks per decade, adult height increased by 2.44 (1.78, 3.10) cm per year higher age at PHV. We found tentative evidence of the positive association between age at PHV and adult height strengthened 0.25 (-0.09, 0.59) cm each decade. Secular trends in related variables may differ if the between-individual and between-cohort associations are different. To understand if a secular trend in one variable has contributed to a trend in another, each needs to be modelled over time, together with the changing association between them.

Minipuberty of human infancy - A window of opportunity to evaluate hypogonadism and differences of sex development?

Activation of the hypothalamic-pituitary-gonadal (HPG) axis happens in 3 phases during life. The first phase is during fetal life and is only separated from the second phase, called minipuberty, by the high concentration of placental hormones at birth. The third period of activation of the HPG axis is puberty and is well-described. Minipuberty consists of the neonatal activation of the HPG axis, mainly in the first 1-6 months, where the resulting high levels of gonadotropins and sex steroids induce the maturation of sexual organs in both sexes. With gonadal activation, testosterone levels rise in boys with peak levels after 1-3 months, which results in penile and testicular growth. In girls, gonadal activation leads to follicular maturation and a fluctuating increase in estrogen levels, with more controversy regarding the actual influence on the target tissue. The regulation of the HPG axis is complex, involving many biological and environmental factors. Only a few of these have known effects. Many details of this complex interaction of factors remain to be elucidated in order to understand the mechanisms underlying the first postnatal activation of the HPG axis as well as mechanisms shutting down the HPG axis, resulting in the hormonal quiescence observed between minipuberty and puberty. Minipuberty allows for the maturation of sexual organs and forms a platform for future fertility, but the long-term significance is still not absolutely clear. However, it provides a window of opportunity in the early detection of differences of sexual development, offering the possibility of initiating early medical treatment in some cases.

References for Ultrasound Staging of Breast Maturation, Tanner Breast Staging, Pubic Hair, and Menarche in Norwegian Girls

CONTEXT

Discriminating adipose and glandular tissue is challenging when clinically assessing breast development. Ultrasound facilitates staging of pubertal breast maturation (US B), but has not been systematically compared to Tanner breast (Tanner B) staging, and no normative data have been reported.

OBJECTIVE

To present normative references for US B along with references for Tanner B, pubic hair (PH), and menarche.

DESIGN, SETTING, AND PARTICIPANTS

A cross-sectional sample of 703 healthy girls aged 6 to 16 years were examined.

MAIN OUTCOME MEASURES

Breast development was determined with US B and Tanner B staging. Tanner PH and menarcheal status were recorded. The age distributions of entry in US B, Tanner B, and PH stages and menarche were estimated with generalized linear and generalized additive models with a probit link. Method agreement was tested with weighted Cohen's kappa.

RESULTS

The median (±2SD) ages for thelarche, US B2 and Tanner B2, were 10.2 (7.7, 12.8) and 10.4 (8.0, 12.7) years. The median (±2SD) ages at Tanner PH2 and menarche were 10.9 (8.5, 13.3) and 12.7 (11.0, 16.2) years. Cohen's kappa of agreement (95% confidence interval) between US B and Tanner B was 0.87 (0.85-0.88). When the methods disagreed, US B was usually more advanced.

CONCLUSION

Thelarche occurred at a slightly younger age when assessed with ultrasound compared to clinical Tanner staging, although the 2 methods had a very good agreement when determining pubertal breast maturation. A significant decrease of 2.8 months in age at menarche was observed during the past decade in Norwegian girls.