What is puberty?
Puberty is a normal and healthy part of growing up and occurs naturally in most people. The changes that happen are prompted by changes in levels of certain hormones produced in the body. Hormones are chemicals that the body produces to send messages around the body. Puberty typically begins around the ages of eight to 14 for most individuals, although the the exact timing varies for each person.
When does puberty happen?
Puberty usually starts between the ages of eight and 13 years in biological females (female sex assigned at birth; referred to as females in this article) and nine to 14 years in biological males (male sex assigned at birth; referred to as males in this article). Each person is unique, so puberty might start at different times and feel different for each individual. Females typically begin puberty before males. However, in recent years, puberty has been starting slightly earlier, especially in females, which might be due to a rise in childhood obesity. The link between obesity and earlier puberty is not fully understood but there are multiple possible reasons. One explanation is the fact that in obesity there is an increase in adipose tissue (fat cells). Adipose tissue produces a hormone known as oestrogen, which is involved in starting puberty in females.
How does it happen?
Puberty depends on the production of several hormones. The types of hormones released will depend on the child’s biological sex and these will also determine the changes the body will go through. In both males and females, when the right age is reached, a special part in the brain called the hypothalamus starts releasing a hormone called kisspeptin (figure 1). This is the ‘starter button’ of puberty. Once released, kisspeptin causes another hormone to be released from the hypothalamus. This hormone is called Gonadotrophin Releasing Hormone (GnRH). GnRH travels to another part of the brain, known as the pituitary gland. There, it instructs the pituitary gland to release two important hormones: luteinizing hormone (LH) and follicle stimulating hormone (FSH). These two hormones signal to the body that it’s time to start puberty. In females, FSH and LH travel through the bloodstream to the ovaries (where eggs are stored) and signal to them to start making the two main hormones in females in puberty, oestrogen and progesterone. In males, FSH and LH travel to the testes (where sperm is made) and tell them to start making testosterone, which is the main hormone responsible for the changes of puberty in males.
Oestrogen and progesterone in females and testosterone in males are responsible for the emotional and physical changes seen in puberty (discussed below).
What happens during puberty?
When puberty starts, individuals experience both physical and emotional changes. Emotional changes sometimes occur before the physical changes.
Both males and females will experience an increase in height (growth spurt), acne (spots) on the face, neck, shoulders, upper back and chest, increased hair growth in the armpits and genitals (usually more in biological males), and emotional changes such as mood swings, and changes in energy levels and sleep patterns.
Biological females also start having periods, experience breast enlargement and tenderness, and widening of their hips. Periods are part of the menstrual cycle, and are a way for the body to get ready to become pregnant in the future. They usually happen monthly, but during puberty they can be irregular (happen less often). Individuals may also notice discharge (thick fluid) from the vagina. This is usually clear or whitish and it is a normal, natural self-cleaning process.
Biologically males will experience muscle growth, voice changes (deeper voice and voice ‘breaking’), hair growth on the face and chest, and growth of the penis and testicles. Individuals also experience erections (hardening and elongation of the penis because blood flow increases) and the production of sperm. Erections can often happen when not expected during puberty. Sperm is made in the testicles and is part of the fluid that ejaculates from the penis (called semen).
Can puberty happen early or late?
Everyone is different and physical and emotional changes can happen at different ages. Sometimes, it can be normal for someone to experience puberty early or late. In some cases, early puberty or delayed puberty could be a sign of an underlying condition that may need treatment.
Early puberty is also called precocious puberty. This is when biological females have signs of puberty before eight years of age and biologically male individuals before nine years of age. It's not always clear what causes early puberty. It often runs in the family (genetic predisposition). Very rarely it can be caused by:
- A brain tumour that produces hormones
- A problem with the ovaries or the thyroid gland
- Genetic (that can be inherited) conditions
To investigate, doctors can carry out physical examinations, blood tests (for hormones), hand X-ray (to look at the bone age), and an ultrasound of the testicles or MRI scan (a special scan) of the brain.
Delayed puberty is when biologically male individuals have no signs of testicular development by 14 years of age and biologically female individuals have not started their periods by 15 years of age. It's not always clear what causes delayed puberty. It may just be a tendency that runs in the family. Delayed puberty is generally more common in boys. Rarely it can be caused by:
- Long term illness, such as diabetes
- Malnutrition (poor nutrition), for example in eating disorders
- Excessive exercise
- Problems with the ovaries, testes, thyroid gland, or pituitary gland
- Genetic conditions
Sometimes individuals with delayed puberty need to be seen by a specialist who carries out investigations (blood test for hormones, hand XRAY, ultrasound, MRI). In delayed puberty the hormones that trigger puberty (LH, FSH, testosterone, oestrogen, progesterone; mentioned earlier) will still be very low or undetectable whereas the levels of these hormones rise as puberty starts.
Delayed puberty can be treated by treating the underlying cause. Sometimes if needed specialists can give hormones to help puberty start.
Conclusion
Puberty marks a significant period of physical and emotional development, triggered by hormonal changes. Alongside the physical and emotional changes, adolescents may also explore for the first time their sexual orientation and gender identity, further adding to the complexity of this developmental stage.
Figure 1: At the start of puberty, kisspeptin is released from the hypothalamus. Once released it stimulates the release of LH and FSH from the pituitary gland. These hormones move to the target organs (testes and ovaries) to stimulate release of testosterone and oestrogen/progesterone respectively. These hormones lead to the changes seen in puberty (in yellow).