Puberty is triggered by hormone signals from the brain to the ovaries and testes (gonads). The ovaries (in girls) and testes (in boys) respond to hormone signals from the brain by producing a range of hormones that stimulate the growth, function and change in various parts of the body, including the reproductive organs, breasts, skin, muscles, bones, hair and the brain.
Growth is fast in the first half of puberty and stops when puberty is completed. Before puberty boys and girls are only different in having different genitalia (sex organs). During puberty several other differences between the sexes start to emerge, including body size, shape, composition and function development in several body systems and structure - we refer to the noticeable differences as secondary sex characteristics.
Puberty also includes the psychological and social changeover from childhood to adulthood. In this article the focus will be more on the physical aspects of puberty, rather than the psychological or social ones.
Many factors can contribute to exactly when puberty begins in a child, even stress. A study found that stress, such as that brought on by parental separation and absentee fathers, fast tracks puberty.
A study by the American Academy of Pediatrics and published in the October 2012 issue of Pediatrics, reported that American boys are reaching puberty between six months and two years earlier than a few decades ago. Doctors had already reported that girls were reaching puberty earlier.
What is the difference between male and female puberty?
- Girls start puberty about one to two years earlier than boys.
- Girls' generally complete puberty in a shorter time than boys.
- Girls reach adult height and reproductive maturity approximately 4 years after the physical changes of puberty appear.
- Boys continue to grow for about 6 years after the first visible changes of puberty.
- A girl's puberty general spans from the ages of 9 to 14.
- A boy's puberty generally spans from the ages of 10 to 17. Experts say this longer span is probably why adult males are generally taller than adult females.
- Testosterone and androgen are the main male sex steroids. Testosterone produces all male changes related to virilization, such as a deepened voice, facial hair and the development of muscles. Estradiol also plays a role in male development, but much more in female development.
- Estrogen and estradiol are the main hormones that drive female development. Estradiol promotes the growth of the uterus and breasts. Levels of estradiol rise earlier in girls than in boys, and also reach higher levels in women than in men. Testosterone is also involved in female development, but to a much smaller degree, compared to male development.
What happens during a girl's puberty?
- Sexual organs - the girl's clitoris (a small and sensitive part of the female genitals which is part of the vulva) and the uterus (womb) will grow.
- Menstruation begins - one of the first things that happens during a girl's puberty is the start of her monthly menstrual cycle. When periods start it means that the girl is becoming a woman and she can become pregnant.
- Breast changes - the girl's breast will start to grow. A small and sometimes painful lump may be felt just below the nipple when her breasts start to develop - this is normal.
- Vaginal discharge - vaginal discharge may start or change.
- Body hair - hair will begin to grow in her pubic area - firstly along the labia (the lips that are part of the external female sexual organs, known as the vulva), and then under her arms and on her legs.
- Skin - as the girl's oil and sweat glands grow her skin will become more oily and she will sweat more. During puberty it is helpful to teach girls about daily washing, and the use of deodorants. Acne is common among girls during puberty.
- Body shape and size - a girl's body changes during puberty. Her hips will widen and her waist will be proportionally smaller. Extra fat will develop on her stomach and buttocks. Girls should not worry about this extra fat - they are part of normal female development and do not mean the girl is getting fat. Her arms, legs, hands and feet will grow - often faster than other parts of her body. It is not unusual for some girls to feel uncomfortable during this stage of development.
- Emotions - a girl's emotions may change, especially around the time her period comes each month. These emotional roller-coaster type changes, which may include irritability, are mainly due to fluctuating hormone levels that occur during the menstrual cycle. If a girl finds her emotional changes become too strong she should consider talking to her doctor - she may be experiencing premenstrual syndrome (PMS) or premenstrual tension (PMT). Health care professionals may be able to help either by prescribing medication or suggesting lifestyle changes. Emotional changes, including PMS are often relieved if the girl takes up regular physical exercise. It may help if the girl can talk to her mother, an older sibling, or another woman about the physical and emotional changes that occur during puberty.
What happens during a boy's puberty?
- Scrotum, testicles and penis - the boy's scrotum will begin to thin and redden and his testicles will grow. Later, usually around the age of 13 (this can vary) his penis will grow and lengthen while the testicles will continue to grow.
- Voice change - as the voice box (larynx) gets bigger and the muscles or vocal cords grow, the boy's voice will "break" or "crack". This is normal. Eventually the boy's voice will become deeper.
- Wet dreams - boys may ejaculate during their sleep and wake up in the morning with damp sheets and pajamas. This does not mean the boy was having a sexual dream. It is important that his loved ones explain to him that they understand that he cannot prevent them from happening. Wet dreams are just part of growing up.
- Involuntary erections - during puberty boys will have spontaneous erections. These will occur without the penis being touched and without sexual thoughts triggering them. These may be embarrassing if they happen in public. This is a natural part of growing up.
- Breast enlargement - swelling of the breasts occurs with many boys during puberty. The boy may feel a bump under one or both nipples - they may feel tender, and sometimes painful. Eventually the swelling and pain will disappear. This is called pubertal gynecomastia and occurs because of hormonal changes during puberty.
- Skin - the boy's skin will become more oily during puberty. He will also sweat much more. During puberty a boy's oil and sweat glands are growing. During puberty it is helpful to teach boys about daily washing to keep the skin clean, and the use of deodorants. It is not uncommon for boys to develop acne during puberty.
- Body size - growth spurts occur during a boy's puberty. This growth peaks at about two years after the onset of puberty. His arms, legs, hands and feet may grow faster than other parts of the body. During this time the boy may feel clumsier than usual. During puberty a boy's total body fat content will start to drop proportionally to his total mass.
- Body hair - hair will start to grow around the pubic area, under his arms, on his legs and arms, and on his face. Facial hair usually starts around the upper lip and chin. This can be shaved off with a razor. Sometimes shaving can cause a rash, especially if the boy has sensitive skin. Using a shaving foam or gel may reduce the chances of getting a rash. Electric razors are less likely to cause cuts.
- Emotions - boys may experience mood swings; one moment they are laughing and then they suddenly feel like crying. Boys may also experience intense feelings of anger. This is partly due to the increased levels of hormones in their body, as well as the psychological aspects of coming to terms with all the physical changes that are taking place. It helps if the boy can talk to a family member, or a good friend. A US study revealed that teenage mood swings may be explained by biological changes in the adolescent brain.
What causes puberty?
- Genes - experts say that puberty starts with a single gene called KiSS1. This gene is present in our bodies at birth and produces another gene called GPR54. GPR54 lies dormant in the body for many years until kisspeptin - chemicals produced by the KiSS1 gene - activate it. Activated GPR54 stimulates the brain to produce GnRH (gonadotropin-releasing hormone) - a powerful hormone. GnRH causes other glands in the body, such as the testes in boys and ovaries in girls to release other hormones.
- Hormones - the testes produce testosterone which encourages the development of the testicles and penis, muscle growth, hair growth, and the deepening of the male voice. The female ovaries also produce testosterone, in much smaller amounts - and it is used to help maintain muscle mass and bone strength. The ovaries produce estradiol which stimulates breast growth, the female reproductive system, as well as regulating the monthly menstrual cycle.
- Triggers of puberty - experts believe environmental and/or genetic factors trigger puberty - even environmental toxins. Nutritional factors are also important, especially for girls. Overweight or obese girls tend to experience earlier puberty, compared to girls of normal weight, while underweight girls tend to start puberty later. Puberty among girls in North America, Western Europe, and several other countries is occurring at an earlier age probably because a higher percentage of them are overweight/obese than before. US scientists have shown that even being overweight as a toddler increases the chance that a girl will reach puberty early. Scientists are not sure whether the timing of puberty is affected by bodyweight in boys.
Diagnosing early or late pubertyA child should only visit a GP regarding his/her puberty if it starts unusually early or late. No signs of breast development by the age of 14 would be an indication of late puberty for girls - or if her breasts have developed but she has had not had a menstrual period by the age of 16. A lack of testicular development by the age of 14 would indicate late puberty for boys - also, if the penis and testicles have not yet reached full adult development since the beginning of puberty.
A GP will order a blood test to find out whether there are any problems with the child's hormones. The doctor may also order an MRI (magnetic resonance imaging) or an ultrasound to check the glands to find out whether they are working properly.
Treatment for early pubertyThe kind of treatment will depend on whether any underlying causes are present. If an underlying condition is detected, that will be treated initially. If no underlying causes are detected there are medications that can temporarily stop puberty from progressing - these medications block the effect of the hormones. Treatment is only recommended if the doctor believes the early puberty may cause problems later in life for the patient, such as weak bones or ending up as a very short adult. If the doctor does not believe there will be problems later on it should not be treated.
A study revealed that early puberty is associated with abnormal eating behaviors and anxiety in young adults.
Treatment for late pubertyLate puberty may have some underlying causes and the doctor will need to find out whether any are present. These may include:
- Eating disorders - such as anorexia nervosa.
- Hormonal conditions - an underactive thyroid gland (Hypothyroidism) may cause puberty to arrive late.
- Other conditions - these may include diabetes, kidney disease, or asthma.
- Genetic conditions - these may include AIS (androgen insensitivity syndrome) - bodies of patients with androgen insensitivity syndrome do not make use of some hormones.
Hormonal changes early in pregnancy cause maternal postpartum anxiety and behavior changes that can lead to a delayed onset of puberty in both birth and adoptive daughters, according to researchers from the University of Otago in Dunedin, New Zealand.