This study conducted a systematic review and meta-analysis to investigate changes in girls’ age at the onset of thelarche (breast gland development) over the past four decades. The findings revealed a significant decrease in the age at pubertal onset, with thelarche assessed through clinical examination, by almost 3 months per decade.

Introduction

A crucial stage in life, puberty, presents both physical and psychological changes. After a period of quiescence during childhood, the hypothalamus-pituitary-gonadal axis reactivates, and the hormone fluctuations during this period of transition ultimately result in the attainment of complete adult reproductive capacity. In females, menstruation is seen as a primary sign of puberty, however, based on research it is a late pubertal phenomenon compared with the development of glandular breast tissue (thelarche) which is an earlier sign of this life stage.

The analysis covered 30 studies from 1977 to 2013, which revealed a significant decrease in thelarche onset by nearly 3 months per decade throughout these years. Secular trends varied based on race, ethnicity, and geography, with the earliest onset observed in the United States and the latest in Africa.

Tanner Scale

Thelarche is represented using the Tanner scale stages where stage 1 represents the prepubertal state and stages 2-5 represent the pubertal stages. The traditional definition of Tanner breast stage 2 involves the initial elevation of both the breast and papilla, along with an enlargement of the areola diameter. Initially, visual inspection was done alone to identify the Tanner scale but now clinical evaluation, integrating both inspection and breast palpation. This approach ensures a reliable distinction between prepubertal and pubertal girls.

The Downward Trend

This study revealed a downward trend in the age of pubertal onset, a reduction of roughly three months per decade. This downward trend has implications for clinical decision-making, as the age at thelarche is a key indicator in distinguishing between early and normal puberty. The study emphasizes the need for updated diagnostic criteria for early puberty, as the traditional definition may no longer be appropriate in certain regions.

What is causing the shift?

Factors such as genetics, nutrition, stress, and environment were considered as potential influences on the onset of puberty. The study highlights the importance of monitoring changes in pubertal timing, not only for clinical purposes but also as a potential indicator of environmental influences on human health.

Conclusion

The study provides valuable insights into changing patterns of thelarche onset in girls, emphasizing the necessity of reevaluating diagnostic criteria and considering environmental factors. Despite some limitations, this study provides valuable insights into the advanced pubertal onset, calling for continued research to monitor and understand pubertal timing changes and their potential long-term health implications.

Significance and Implications

• Assessing breast development in girls is crucial for distinguishing between normal and early puberty.
• Changes in thelarche onset impact diagnostic decision-making in girls suspected of puberty disorders.
• This study prompts a reevaluation of traditional definitions of early puberty, particularly considering the global obesity epidemic and the daily exposure to endocrine-disrupting chemicals.
• Highlights geographical variations in the age of thelarche, emphasizing the importance of considering regional differences.

Reference

Eckert-Lind C, Busch AS, Petersen JH, et al. Worldwide Secular Trends in Age at Pubertal Onset Assessed by Breast Development Among Girls: A Systematic Review and Meta-analysis. JAMA Pediatr. 2020;174(4):e195881. doi:10.1001/jamapediatrics.2019.5881

NHS. (n.d.). Changes for girls. NHS choices. https://www.fresh4manchester.nhs.uk/find-out-the-facts/puberty/changes-for-girls/