Recognizing puberty onset in boys

While mood swings may be the first sign parents notice when it comes to the onset of male puberty, there are several clinical features that pediatricians can use to gauge where their patients are in this process.

Katherine Kutney, MD, a pediatric endocrinologist and assistant professor of the field at Rainbow Babies and Children’s Hospital in Cleveland, Ohio, said that for both boys and girls, the whole process is triggered by the activation of the hypothalamic-pituitary-gonadal ( HPG) axis. In boys, this causes testicular growth, which is the first clinical sign that a man has entered central puberty.

The first clinical sign that this process has begun is an increase in testicular volume of 3 ml or more. An increase in height will occur when the testicular volume reaches 10-12 ml, Kutney said. Men who have reached this testicular volume without a growth spurt may be cause for concern, she added.

In addition to central puberty and the increase in testicular volume, another process is underway. This process, adrenarche, begins with the production of adrenal androgens. Commonly referred to as male sex hormones, these hormones stimulate the growth of pubic hair, armpit hair and acne during puberty.

Kutney said that while central puberty and adrenarche often occur together, these two processes are regulated separately and it is possible to have one without the other.

This is especially true when puberty starts earlier than the normal range for boys, which is between the ages of 9 and 14, or on average by 11 years of age. Studies have suggested that girls enter puberty earlier than previous generations, but whether the same is true for boys is still open to question.

A 2012 report in Pediatrics found that boys started experiencing testicular volume gain and pubic hair growth six months to two years earlier than in previous studies.1 Many of the studies on which the male average was based were based only on white, European boys. The 2012 study took into account different ethnicities, pointing to earlier genital and public hair development in African American boys compared to Caucasian and Hispanic boys.

The study points out the limitations based on the fact that previous studies generally did not include non-white boys. However, looking only at sexual development in white boys, the 2012 study found that white boys entered stage 2 genital growth on the Tanner scale about 1.5 years earlier — from 10.14 years in the 40-year-old UK study up to 11.6 years in 2012 US study.

A more recent study, published in JAMA Pediatrics in 2019, appears to confirm boys’ earlier onset of puberty.2 The 2019 study found that a number of factors may account for this shift, but points to an increase in body size. mass index in children. as at least a partial cause.

While the exact cause of earlier puberty in boys has yet to be determined, experts still agree that the Tanner Staging, or Sexual Maturity Rating scale, is still the most reliable and objective rating system for onset and progression. by determining puberty. The system takes into account the development of both genital and pubic hair to determine the staging.

For boys and girls, stage 1 of the Tanner scale denotes the pre-pubertal period and stage 5 means full sexual maturity. A clinical reference of Tanner stages for boys is below

Tanner Staging for Men

Pubic hair

Stage 1: no hair Stage 2: light, fluffy hair Stage 3: thicker, darker (terminal) hair begins to develop Stage 4: terminal hair covers the entire pubic triangle Stage 5: terminal hair covers the entire pubic triangle and extends beyond the groin fold to the thigh

genitals scale

Stage 1: Testicular volume of less than 4 ml, or long axis of less than 2.5 cm Stage 2: Testicular volume of 4-8 ml, or long axis of 2.5 to 3.3 cm in length Stage 3: Testicular volume of 9-12 ml, or a long shaft 3.4 to 4 cm long Stage 4: Testicular volume of 15-20 ml, or a long shaft between 4.1 and 4.5 cm in length Stage 5: Testicular volume of 20 ml or more, or a long axis more than 4 cm long


1. Herman-Giddens, et al. Secondary Sex Characteristics in Boys: Data from the Pediatric Research in the Network of Office Institutions. Pediatrics. 2012;130(5): e1058-e1068. doi: 10.1542/peds.2011-3291

2. Ohlsson C, Bygdell M, Celind J, et al. Secular trends in pubertal growth acceleration in Swedish boys born from 1947 to 1996. JAMA Pediatr. 2019;173(9):860-865. doi:10.1001/jamapediatrics.2019.2315

3. Emmanuel M, Bokor BR. Tanner stages. Stat Pearls Publishing. 2021

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