Puberty is not the same for everyone. The age it starts, when it ends and the changes that occur are all different from person to person.
When does puberty start for boys?
Puberty usually starts sometime between the ages of nine and 14 years for boys. It lasts for about five to six years.
Boys who begin puberty early (before nine years of age) may have an underlying medical cause that might need treatment. For some boys, puberty might begin normally but then stop — this is common in Klinefelter syndrome. If puberty begins early or does not progress normally, you should see a doctor because treatment is often necessary to avoid long-term health problems.
Stages of puberty for boys
We often think of puberty in terms of the physical changes that happen. Doctors refer to ‘Tanner stages’ of puberty, which describe stages of development of the genitals and pubic hair. There are also important changes that occur in the brain during puberty, which are responsible for changes in emotions, thinking and behaviour. These changes to the brain occur over a span of more than 10 years and continue past 20 years of age.
Tanner stage 1
This is the pre-puberty stage, when the genitals are child-like, there is no pubic hair and the size of the testes is less than 4 ml in volume (the longest measurement along the centre of the testis is less than 2.5 cm).
Body shape is child-like, and height increases by about one cm every two months.
During this stage, self-awareness begins to develop, but thinking is very straightforward and matter-of-fact. There is a basic understanding of others’ thoughts and feelings.
Tanner stage 2
Testosterone production by the testes begins, and the testes get bigger (about 4 ml in volume; longest measurement along the centre is 2.5-3.2 cm). The scrotum starts to grow and its skin becomes thinner and redder. Fine, soft hair begins to develop at the base of the penis, but the size of the penis has not changed much if at all.
Height increases by around one cm every two months, and body shape hasn’t changed much.
The hormonal changes during this time can cause mood swings, and there might be more desire for independence and privacy, and self-consciousness about appearance. Problem-solving skills and impulse control begin to develop, along with personal opinions and questioning of authority. Risk-taking, thrill-seeking and rule-breaking begin to increase.
Tanner stage 3
Testosterone levels increase. Growth of the testes (volume 6-12 ml, longest measurement about 3.6 cm) and scrotum continues, and the penis begins to grow in length. Pubic hair becomes darker, coarser and curlier and begins to spread over a wider area.
Body growth begins to accelerate. Height increases by 1.5 cm every two months, the shoulders begin to broaden and muscle mass increases. Development of breast tissue (gynaecomastia) may occur (this usually goes away on its own as puberty progresses).
Acne may begin, the voice might begin to break, and spontaneous erections (and ejaculation during sleep) may begin.
Mood swings, emotional outbursts, frustration, irritability and anger are linked to rising testosterone levels during this time. The desire to fit in with peers increases, and focus shifts from family to friends.
The frontal lobe of the brain is still immature, so judgment, impulse control and planning skills are limited. Reasoning skills and the use of logic develop. Awareness and interest in thinking and the future begin. The ability to reason about other people’s thoughts and infer hidden meanings increases.
Risk-taking and thrill-seeking increase.
Tanner stage 4
Testosterone levels are at their peak. The testes continue to grow (12-20 ml, longest measurement 4.1-4.5 cm) and the scrotum gets larger and darker. The penis grows in length and width. Pubic hair is adult-like but has not spread to the inner thighs.
Body growth peaks with height increasing by almost one cm per month, as bone and muscle growth increase.
Hair develops in the armpits, the voice deepens and acne may increase.
Sperm development begins, so fertility is reached during this stage.
Emotional intensity and complexity are at their highest. Periods of sadness and confusion may be common, social or sexual anxiety may develop and feelings of rejection may occur. Experimentation with identity by changing appearance or behaviour may occur.
The ability to analyse things develops, reasoning skills improve (but might be inconsistent), and systematic thought about the future and planning begins. The ability to interpret non-verbal cues (e.g. facial expressions, body language) increases.
Risk-taking behaviour is greatest during this stage, with potentially negative (substance use, physical recklessness, aggression) and positive (trying new physical, social and academic activities).
Tanner stage 5
Maturation of the reproductive system is achieved, including hormonal regulation and the growth of the penis, scrotum and testes (volume greater than 20 ml; longest measurement greater than 4.5 cm).
An adult physique is achieved as full height is reached, but muscle growth continues beyond puberty.
Facial hair develops, and gynaecomastia and acne may disappear.
As the brain completes maturation, emotional regulation improves and mood swings reduce. A stronger sense of identity develops, personal values are established, and relationships with friends and sexual partners become more stable.
Abstract thought develops, allowing the interpretation of meaning, finding patterns, connecting ideas and seeing the big picture. The ability to control and coordinate thoughts and behaviour continues to develop beyond puberty, as do social skills.
Risk-taking begins to decrease as impulse control increases and reasoning skills improve, leading to better risk assessment and decision-making.
Tim Moss
Healthy Male Health Content Manager
Associate Professor Tim Moss has PhD in physiology and more than 20 years’ experience as a biomedical research scientist. Tim stepped away from his successful academic career at the end of 2019, to apply his skills in turning complicated scientific and medical knowledge into information that all people can use to improve their health and wellbeing. Tim has written for crikey.com and Scientific American’s Observations blog, which is far more interesting than his authorship of over 150 academic publications. He has studied science communication at the Alan Alda Centre for Communicating Science in New York, and at the Department of Biological Engineering Communication Lab at MIT in Boston.
