From boy to man

Kathrin Rothfischer studied microbiology and genetics in Regensburg after an excursion into German studies. Presenting complex issues in an easily understandable way was her passion even then. That is why she turned this passion into a profession after graduating: After various positions in the medical specialist publishing house and in the public press, she finally found her journalistic home at

More about the experts All content is checked by medical journalists.

Most boys want to be cool, muscular and finally grown up. When boys become men, the hormones take control of your body first. That can be annoying, but sometimes also very exciting. And at least there is some consolation: not only you, all your friends will hit puberty sooner or later.

Hair - more or less

The hormone testosterone is responsible for most of the changes. The first sign that your boy-to-man transformation has begun is hair that begins to grow around your penis and testicles. For some boys this can happen at the age of nine, for others only at 14 - everything is normal! At the same time, sometimes a little later, you get armpit hair. Only then do the beard hair and other body hair, for example on the chest or back, usually start to sprout. How hairy you end up being depends on your genes. Some boys and men have little beard and hardly any chest or back hair, which is also normal.

Growth chaos

You can also hear from your voice that your body is currently in a phase of upheaval. When the voice breaks, it can sound hoarse and is not so resilient. This is because your larynx is getting bigger. The cartilage increases in thickness and strength, and the vocal folds become longer. All of this makes your voice sound more masculine, i.e. deeper.

But not only the larynx grows, the rest of the body also grows. The order is a bit mixed up. First come the head, feet and hands. Only then do the arms and legs shoot out and, at the very end, the upper body. Your body may look a little unbalanced in its proportions during this time. At the latest when the growth phase is over, it will have subsided.

Your body not only grows when you go from boy to man, it also changes its composition. That means: the muscle percentage becomes higher, shoulders and chest become wider.

Sometimes it happens that your body makes a lot of testosterone during puberty and then converts the excess hormone into estrogen. Many boys do not find what happens then that great: they develop breasts! Sounds incredible, but it's true. This is called "puberty gynecomastia". But don't panic: at the end of puberty, your breasts will disappear and your breasts will look completely normal.

Penis problems

Your physical development during puberty also includes changes in the external genitals, i.e. the penis and testicles. Sometimes one testicle hangs lower than the other. But that is no cause for alarm, many boys and men have it. It even makes sense because the two testicles are not constantly pressed against each other when walking or running. The penis also looks different in everyone. And its growth is only complete at the age of 16 to 18.

When you are sexually aroused, your penis becomes stiff. This is also called an erection. A stiff (erect) penis is only in the rarest of cases completely straight. Mostly it has a slight curvature and the angle at which it protrudes from the body is different for every man.

Your penis is particularly sensitive to touch, especially the tip (glans). But also an attractive sight or arousing thoughts can cause it to become stiff. Sometimes it just happens for no particular reason and in inappropriate situations. You don't have to be embarrassed, because your body reacts completely normally.

Wet dreams

Surely you've heard of "wet dreams" before. Seminal fluid comes out of the penis at night. This fluid contains millions of sperm cells, also called sperm. When the fluid comes out of the penis, it is also called ejaculation or ejaculation. The wet dreams are the first sign that you are sexually mature and theoretically able to father a child.

By the way, many boys are concerned that during ejaculation, for example when they sleep with a girl, urine will also leak from the penis. However, that is impossible. You can't pee with a stiff penis. Conversely, there is no ejaculation when the patient is flaccid. So you don't need to worry about that.

Tags:  fitness Menstruation foot care