The 5 Stages of Puberty in Boys

How Your Son Develops Into a Young Man

Teenage boy exercising with dumb bell
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A boy goes through many important changes during puberty. His body beefs up, his voice cracks as it changes, he becomes stronger, and he begins to mature sexually. Before you know it, your little boy has become a young man. There are five stages of puberty that boys go through, but keep in mind that the age at which each boy goes through them can vary widely.

Signs of Puberty in Boys

Boys mature a little slower than girls. For 95 percent of boys, puberty begins around age 9 but may start as late as age 14. Some boys mature faster than their peers, and some physical changes may be more gradual than others.

A number of these physical changes are very personal. As a parent, you may not notice them, but your son will. Some of these may be embarrassing experiences for him and he will likely keep much of this private.

Body Shape

Externally, you may notice your son's body begin to grow, but just before that happens, he may put on a little weight and look like he's all arms and legs. Next comes a growth spurt, often around the age of 15. His shoulders will broaden and his muscles will develop more definition too. He will become noticeably stronger and can take advantage of that by beginning a regular workout routine.

Sweating, Hair, and Acne

Personal hygiene is probably one of the biggest changes for young boys. It may have been hard to get him to wash his hands or take a shower, but now he will need to pay attention to these things as he starts to sweat more and develop body odor. He may soon come to you and ask about shaving the peach fuzz from his face or ask about antiperspirants. His hormones will produce more oil on his skin and he may be prone to acne breakouts. This is the perfect time to introduce him to good skin care routines.

Penis and Testicle Growth

The first sign of puberty actually begins with the growth of your son's testicles and scrotum, which will eventually nearly double in size. His penis and testicles will begin to grow as he enters puberty too, as will his pubic hair. The penis begins by growing in length, followed by width. You can find more details on this growth in the Tanner stages section below.

Around one-third of boys have tiny pearly bumps, called papules, on their penises. These bumps look like pimples and are normal and harmless, though they are permanent.

Nocturnal Emissions and Erections

As your son develops, he may begin to have nocturnal emissions, or "wet dreams," in which he ejaculates at night. This can occur with or without a sexual dream and is completely normal. Talking to your son about nocturnal emissions before they happen is helpful so he knows what to expect and that he hasn't accidentally wet the bed. Let him know that it's just another part of puberty and that it'll go away in time.

Involuntary erections are another big part of male puberty and they can occur at any time, for absolutely no reason at all. Explain to your son that this may happen for awhile, and he will likely have little control over it, but it will get better as he gets older.

Voice Change

Your son's voice will change around the time that his growth spurt has begun to slow down a bit. This occurs because his vocal chords and voice box (larynx) grow too. Before his voice changes completely, it may crack and soar, going from high to low quickly. This can be embarrassing for him, so be mindful of this.

Breast Growth

When your son is first in puberty, his breast tissue may swell a bit for a year or two as some of his hormones change into estrogen. For the majority of boys, this is temporary and not excessive, though in some boys, it can be more obvious, especially if they're overweight. If your son's breast area seems excessively swollen or the swelling happens before puberty or later in puberty, see your healthcare provider. There could be a medical problem that's causing this swelling rather than hormones.

Mood Swings

Like girls, boys can also have mood swings thanks to the hormonal, physical, and emotional changes they're experiencing. Be patient and understanding; this, too, shall pass.

Talking to Your Son

Your little boy is growing up and this also means that he may open up to you less often. It's common for teenage boys to become less talkative and withdraw from their parents. Keep the lines of communication open and talk to your son about the changes he's experiencing. Stay connected to his interests and talk to him about sports, school, or whatever he enjoys. This will help him feel comfortable about coming to you when he needs to talk about something important.

Tanner Stages of Sexual Development

Teen boys will develop physically in certain stages, often called Tanner stages. Your pediatrician or family healthcare provider can determine what stage your teen is at and if it's expected for his age. The Tanner stages, along with approximate age ranges, include:

  • Sexual Maturity Rating 1: The prepuberty stage. The testes are small and the phallus (penis) is child-like. There is no pubic hair.
  • Sexual Maturity Rating 2: From 9 years old to 14 years old. The testicles grow in volume and size. The penis has no to slight enlargement. The scrotum becomes reddened, thinner, and larger. A few pubic hairs become visible and they are long, straight, and slightly dark.
  • Sexual Maturity Rating 3: From 10 years old to 14 years old. The testes continue to grow in volume and size. The penis becomes longer. The scrotum continues to enlarge. Pubic hairs become darker and curlier and more of them appear.
  • Sexual Maturity Rating 4: From 11 years old to 15 years old. The testicles continue to grow. The penis continues to grow in length and now becomes thicker. The scrotum grows larger and also darkens. Pubic hair is coarse, thicker, and curly like adult hair, though there are fewer hairs than an adult has.
  • Sexual Maturity Rating 5: The testicles are of an adult size (greater than 20 ml in volume). The scrotum and penis are of adult size and form. The pubic hair is of normal adult distribution and volume.

    Delayed Puberty

    If your son hasn't started puberty by the age of 14, which means that his testicles and penis haven't started to grow yet, this is considered delayed puberty. The most common cause is called constitutional delayed puberty. Most boys who are constitutionally delayed are totally healthy and will go through puberty eventually. Two-thirds of boys inherit this from one or both of their parents who also started puberty late. In men, this can be defined as having a growth spurt after the age of 16 years old or continuing to grow after high school. In women, delayed puberty is starting menstruation after the age of 14 years. The majority of boys who are constitutionally delayed are also short compared to other boys their age, but this is just because they haven't had their growth spurt yet.

    If your son has a chronic illness like sickle cell disease, inflammatory bowel disease, or cystic fibrosis, puberty may also begin later than normal.

    A small number of boys have a condition called isolated gonadotropin deficiency (IGD), which means that they don't produce adequate amounts of the hormones LH and FSH. This condition typically begins at birth and is typically treated with testosterone injections.

    An even smaller number of boys have something going on with their testicles that's causing puberty to be delayed. Testosterone is the main treatment for issues of this sort.

    A Word From Verywell

    If you have questions or concerns about how your son is progressing through puberty, talk to his healthcare provider. Your doctor can determine if your teen is growing and developing as expected and help you understand the biology that's at work. In the case of suspected delayed puberty, it's possible that your son's penis and testicles have gradually started to enlarge and he just hasn't noticed. Your doctor can tell with a physical exam and can run some tests on your son's hormones to see if there are any problems.

    View Article Sources
    • Kliegman, RM. et. al. Nelson Textbook of Pediatrics. Elsevier; 2016.
    • Neinstein LS, Katzman DK. Neinsteins Adolescent and Young Adult Health Care: a Practical Guide. Philadelphia: Wolters Kluwer; 2016.
    • American Academy of Pediatrics and Pediatric Endocrine Society. Delayed Puberty in Boys: Information for Parents. HealthyChildren.org. Updated June 9, 2015. https://www.healthychildren.org/English/ages-stages/gradeschool/puberty/Pages/Delayed-Puberty.aspx
    • American Academy of Pediatrics and Pediatric Endocrine Society. Physical Development in Boys: What to Expect. HealthyChildren.org. Updated May 22, 2015. https://www.healthychildren.org/English/ages-stages/gradeschool/puberty/Pages/Physical-Development-Boys-What-to-Expect.aspx