Puberty is the process by which the body transitions from childhood to sexual maturity, driven by a cascade of hormonal changes that begins in the brain and ripples through virtually every system in the body. It is not simply about physical development; it involves significant shifts in mood, behaviour, sleep, appetite, and the emerging sense of identity. For young people going through it and parents watching from the outside, having a clearer picture of what's actually happening is considerably more useful than the limited biology lessons most people received.
Puberty typically begins between ages 8 and 13 in girls and 9 and 14 in boys, though the range of normal is wide. Starting earlier or later than peers can itself be a source of anxiety, and it's worth knowing that significant variation is normal.
The hormonal trigger
Puberty begins when the hypothalamus starts releasing gonadotropin-releasing hormone (GnRH), which signals the pituitary gland to produce luteinising hormone (LH) and follicle-stimulating hormone (FSH). These hormones in turn stimulate the ovaries or testes to produce oestrogen and testosterone respectively. Both sexes produce both hormones; the balance differs.
In girls, rising oestrogen drives breast development, growth of the uterus and ovaries, redistribution of body fat, and eventually the onset of periods. In boys, rising testosterone drives testicular growth, a deepening voice, increased muscle mass, and the production of sperm. Both sexes experience growth spurts driven partly by growth hormone and partly by sex hormones, as well as the development of pubic and underarm hair driven by androgens from the adrenal glands.
"Puberty is a biological process, but it's also a psychological one. The brain is changing as much as the body, and the emotional intensity that comes with that is entirely expected."
The brain in puberty
One of the less discussed aspects of puberty is the profound changes happening in the brain. The prefrontal cortex, responsible for judgement, impulse control, and long-term planning, is one of the last areas to fully mature, not completing development until the mid-twenties. During puberty, the emotional and reward centres of the brain are highly active while the regulatory systems are still catching up. This explains a great deal about adolescent behaviour: the intensity of emotion, the risk-taking, the reactivity, and the seemingly inexplicable mood swings are neurological realities, not personality flaws.
Sleep patterns also shift significantly during puberty due to changes in melatonin production. The circadian rhythm moves later, making it biologically harder to fall asleep early and harder to wake in the morning. This is a genuine physiological shift and not simply laziness or defiance.
Periods: what's normal and what isn't
The first period, or menarche, typically arrives around two to three years after breast development begins. Cycles are often irregular in the first year or two as the hormonal system establishes itself. Heavy periods, significant pain, or cycles that remain very irregular beyond the first two years are worth discussing with a GP, as they can indicate conditions such as polycystic ovary syndrome or endometriosis that benefit from early identification.
Supporting young people through puberty
Open, factual conversations about what's happening physically and emotionally tend to make puberty considerably less confusing for young people. Normalising the changes, including the emotional intensity and the awkwardness, rather than treating them as problems to be managed, is one of the more useful things adults around them can do. Access to accurate information, without shame or embarrassment attached, gives young people the foundation to understand and look after their own bodies.
If a young person is experiencing significant difficulties during puberty, whether physical symptoms that seem unusual or emotional distress that's affecting their daily life, a GP is the right first step. A therapist experienced in working with young people can also be a useful support. Welvow can help find relevant practitioners in your area.
Find your practitioner →Puberty is demanding for most young people. Good information and open communication make a real difference to how they experience it.