Son Has Questions About Puberty

Our expert answers some common questions about puberty in boys.
My 13-year-old son has a few questions about puberty:

  1. How long does it last and at what age does it start?
  2. What are some of the signs that he has started puberty?
  3. He is concerned with what size his penis should be. How does he know if it's too small?
The age at which puberty can start varies a great deal. This can cause some kids to worry if they are a little later than their friends, but earlier is not better than later, and vice versa. In boys, puberty takes about five years to complete, going from the time of the first noticeable changes to a full grown adult. The average age for starting puberty is 11, but it can be as early as 9 or as late as 14.

The first physical change that you can see in the genitals is that the testicals start to enlarge. The scrotum (the sack containing the testicals) may begin to look more red or dark, and "wrinkly" in appearance. Next, the penis starts to get longer and larger. A few strands of pubic hair often develop at this time, as well. All of these processes continue over the course of the next several years, and take a while to complete. The penis does not reach its full adult size until the end of puberty. There is no "right size" for the penis to be. Just as people have different foot sizes and head sizes, they have different penis sizes. Larger is not any better than smaller. As long as the penis does begin to grow from its pre-puberty size, there is no reason for concern.

There are many other changes apart from the physical growth of the genitals. During the middle of puberty, boys may notice that their voice "cracks" as it begins to become deeper. Hair begins to develop under the arms and grow on the legs. Boys will have involuntary erections that they have no control over, as well as ejaculations in their sleep that they are not aware of. This can be concerning to some boys and their parents, but it is all perfectly normal and expected.

The other major change that is occurring during puberty is a growth in height, as well as muscle mass. This aspect of change does not occur until the later half of puberty in boys, so it is quite typical to see that many girls are taller than the boys in 5th through 8th grades, as the girls have their growth spurt earlier.

Shari Nethersole is a physician at Children's Hospital, Boston, and an instructor in Pediatrics at Harvard Medical School. She graduated from Yale University and Harvard Medical School, and did her internship and residency at Children's Hospital, Boston. As a pediatrician, she tries to work with parents to identify and address their concerns.

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