Lead
One morning, while helping your child get dressed, you notice a body that looks subtly different from a few weeks ago. You find yourself wondering — when did that change? And then the questions: Is this too early? Or is this within the normal range?
This article introduces the Tanner staging system — the clinical framework used to assess pubertal development — explains how growth spurts relate to that framework, and outlines when to consider a medical evaluation for early or delayed puberty. The goal is to give you a reference point for making that judgment, not a prescription.
Background
The clinical scale most widely used to assess puberty is Tanner staging: a five-stage clinical scale (B1–B5 for breast, G1–G5 for genitals, P1–P5 for pubic hair) that classifies pubertal development into objective, observable stages (Sexual Maturity Rating, or SMR), established by Marshall and Tanner in the 1960s [1]. It classifies breast development (B1–B5) and pubic hair (P1–P5) in girls, and testicular volume (G1–G5) and pubic hair in boys — describing visible physical changes not as a subjective impression but as objective stages.
Among Japanese girls, the median age at menarche was approximately 13.8 years for those born in the 1930s, fell through the 1950s and 1960s, and has remained relatively stable at around 12.2–12.3 years since the 1990s [2,3]. This figure serves as one reference point for judging whether a given timing is considerably early or considerably late.
The timing of the growth spurt — Peak Height Velocity, or PHV — also maps onto Tanner staging. In girls, PHV typically occurs between Tanner B2 (the beginning of breast development) and B3, approximately one to one and a half years after puberty begins [4]. Boys reach PHV between Tanner G3 and G4, on average about two years later than girls. This means that a sense of "the growth spurt slowing down" can serve as a backwards indicator of where in puberty a child currently sits.
The Growth Spurt Comes Before You Expect It
For many parents, the most counterintuitive point is that the growth spurt arrives before the changes they tend to notice.
In girls, PHV typically occurs six months to a year after breast development begins (Tanner B2), and menarche follows after PHV [4]. In other words, by the time a girl has her first period, the most rapid phase of height gain has already passed.
For parents who are hoping their child will still grow taller, knowing this sequence improves the quality of their judgment. If height has been measured consistently twice a year or more, the shape of the growth curve becomes readable — even in retrospect. Using an app like Memori to log height at regular intervals lets you trace, after the fact, when growth accelerated and when it began to plateau.
Precocious Puberty — Where to Set the Threshold
In Japan, the clinical referral threshold for central precocious puberty (CPP) is breast development before age 7 years 6 months in girls, or menarche before age 10 years 6 months [3].
One trend worth noting: research by Iwama and colleagues reported an increase in CPP diagnoses in Japan during 2021–2022, in the period following the COVID-19 pandemic [5]. The debate around causation focuses not on infection itself but on reductions in physical activity, disruptions to daily routine, and rising BMI during that period.
The concern with precocious puberty is not only the psychosocial stress associated with physical changes that set a child apart from peers. Early closure of the growth plates driven by sex hormones can reduce final adult height. Evidence on longer-term metabolic and psychological consequences continues to accumulate [6], and these changes are not ones to dismiss without evaluation.
If you notice breast changes before age 8, or pubic hair before age 7, it is worth considering a specialist evaluation sooner rather than later.
Delayed Puberty and Constitutional Delay — When to Watch and When to Investigate
When puberty appears delayed, the most common explanation is Constitutional Delay of Growth and Puberty (CDGP). CDGP is the leading cause of delayed puberty, estimated at over 2–3% of the population, and occurs predominantly in boys [7,8].
CDGP usually resolves on its own — the prognosis is good, and puberty completes spontaneously in most cases. However, children with CDGP frequently experience psychosocial stress: being perceived as younger than their peers, or discomfort in changing rooms. Attention to that stress remains necessary even in cases where watchful waiting is medically appropriate [8].
The medical referral thresholds are: in boys, testicular volume remaining below 4 mL after age 13; in girls, absence of menarche at age 16 [7,8]. These are reference points, not bright lines that guarantee "everything is fine before this." But they are useful as anchors for decision-making.
If delayed puberty is a concern, the most useful first step is a visit to a pediatrician to request a bone age assessment. The earlier that step is taken, the less is lost.
Putting It Into Practice
Pubertal changes are not all visible to a parent. But if records exist, the trajectory can be read after the fact.
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Measure height twice a year, in the same spot, and log the difference from the previous reading. A growth spurt shows up as a sharp upward step. Starting from the moment you notice is not too late.
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If you notice breast changes before age 8, or menarche around age 11, bring that information to your child's next pediatric appointment. Not as an emergency, but as a piece of data to share with the clinician — with a record in hand to show when the change began.
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If you suspect delayed development, a bone age evaluation at a pediatrician's office is the appropriate first option. Observation and professional assessment are not in conflict.
Knowing that breast development (Tanner B2) precedes the growth spurt by one to one and a half years changes how you read the changes you are seeing.
Summary
Puberty unfolds in stages, not all at once. Having the Tanner staging framework as a reference allows "early" and "late" to be communicated to a physician not as impressions but as clinical descriptors. The referral thresholds — breast development before age 7 years 6 months in girls, testicular volume below 4 mL after age 13 in boys — function as an entry point for clinical judgment, not as the only signal worth acting on.
If records exist, both a sharp growth acceleration and the timing of any change become readable after the fact. The moment you notice a change is precisely the right moment to start keeping one.
References
- Rogol AD, Clark PA, Roemmich JN. Growth and pubertal development in children and adolescents: effects of diet and physical activity. StatPearls. 2023. NBK470280.
- Hata K, Aoki S, Hata T, Kitao M. Secular trend of the age at menarche of Japanese girls with special regard to the secular acceleration of the age at peak height velocity. Hum Biol. 1981;53(4):593–600. PMID: 7327541.
- Matsuo N. Secular trends in age at menarche and time to establish regular menstrual cycling in Japanese women born between 1930 and 1985. BMC Womens Health. 2012;12:19. doi:10.1186/1472-6874-12-19. PMID: 22800445. PMC: PMC3434095.
- Biro FM, Huang B, Chandler DW, Kiess W, Dorn LD, Pinney SM. Relationship between timing of peak height velocity and pubertal staging in boys and girls. J Adolesc Health. 2016;58(6):710–716. doi:10.1016/j.jadohealth.2016.01.014. PMID: 26831559. PMC: PMC4677560.
- Iwama S, Arima H, Fujisawa H, et al. Trends in central precocious puberty incidence in Japan during the COVID-19 pandemic. Front Pediatr. 2026;14:1769902. doi:10.3389/fped.2026.1769902.
- Gawlik A, Gawlik K, Wolny D. Early puberty: a review on its role as a risk factor for metabolic and mental disorders. Arch Med Sci. 2024. PMC11424421.
- Zhu J, Chan YM. Adult consequences of self-limited delayed puberty. Pediatrics. 2017;139(6):e20163177. doi:10.1542/peds.2016-3177. PMID: 28557726. / Zhu J, Chan YM. Delayed puberty including constitutional delay: differential and outcome. Front Endocrinol. 2024;15:1391506. doi:10.3389/fendo.2024.1391506. PMID: 38677869.
- Howard SR, Dunkel L. Current clinical management of constitutional delay of growth and puberty. Horm Res Paediatr. 2022;95(4):340–350. doi:10.1159/000520413. PMID: 35331309. PMC: PMC8944060.