Delayed Puberty in Girls and Boys

What counts as delayed puberty

Puberty normally begins between 8 and 13 in girls and 9 and 14 in boys. Delayed puberty is defined statistically: it is when development starts later than in about 97 to 98 out of 100 children of the same sex.

Pubic hair alone does not count as the start of puberty, because it is driven by adrenal hormones and can appear without true puberty.

Signs of delayed puberty

• Girls: no breast development, no growth spurt, no periods.
• Boys: small testicles and penis, no voice change, little body hair, no growth spurt.
• Both: being noticeably shorter and younger-looking than classmates, with slower growth, often around 5 cm (2 inches) a year or less.

Many teens find this hard emotionally. Teasing, low self-esteem and avoiding sports or changing rooms are common, and these are valid reasons to seek assessment.

Causes of delayed puberty

Constitutional delay (the commonest cause)

Constitutional delay of growth and puberty is a variation of normal timing. These children are healthy but have a slower biological clock. They are often small for their age through childhood, with a bone age 1 to 3 years behind their actual age, and usually have a parent who was also late (a father who grew after high school or a mother with late first periods). Puberty starts on its own, and final adult height is usually within the expected family range, though sometimes slightly lower. It accounts for most boys and a smaller share of girls with delay.

Temporary hormone suppression (functional causes)

The brain switches off puberty hormones when the body is under strain:

• Chronic illness: celiac disease, Crohn's disease, cystic fibrosis, kidney disease, poorly controlled diabetes, sickle cell disease and severe asthma.
• Low energy availability: anorexia nervosa, undernutrition, and intensive training in sports such as gymnastics, ballet and distance running.
• Hypothyroidism: an underactive thyroid slows growth and development.
• High prolactin: from a pituitary tumor or some medicines. See hyperprolactinemia.
• Severe stress and some medicines.

Puberty usually starts once the illness or energy deficit is corrected.

Brain or pituitary causes (low signal from the brain)

Called hypogonadotropic hypogonadism, this is when the hypothalamus or pituitary does not send the hormones LH and FSH that start puberty:

• Kallmann syndrome: a genetic condition with delayed puberty and a missing or reduced sense of smell.
• Isolated GnRH deficiency with a normal sense of smell.
• Pituitary or brain tumors such as craniopharyngioma, often with headaches, vision changes and slow growth.
• Damage from brain radiation, surgery or head injury.
• Growth hormone deficiency and multiple pituitary hormone deficiencies.

Ovary or testicle causes (high signal from the brain)

Called hypergonadotropic hypogonadism, this is when the brain signals normally but the ovaries or testes do not respond:

• Turner syndrome: a missing or altered X chromosome in girls, with short stature and ovaries that fail early.
• Klinefelter syndrome: an extra X chromosome in boys. Puberty often starts but stalls, with small, firm testes.
• Damage from chemotherapy or radiotherapy.
• Undescended testes, testicular torsion or mumps orchitis.
• Autoimmune ovarian failure and galactosemia.

How doctors assess delayed puberty

1. History: family timing of puberty, birth history, illnesses, diet and exercise, medicines, sense of smell, headaches and mood.
2. Growth chart: plotting height and weight over years shows whether growth is steady or slowing.
3. Examination: puberty staging (Tanner stages), testicular volume, body proportions and features of genetic syndromes.
4. Bone age X-ray: an X-ray of the left hand and wrist estimates skeletal maturity. A delayed bone age supports constitutional delay.
5. Blood tests: LH, FSH, testosterone or estradiol, thyroid function, prolactin, IGF-1, a full blood count, inflammatory markers and a celiac screen.
6. Further tests: chromosome testing (karyotype) when LH and FSH are high, and MRI of the brain and pituitary when a central cause is suspected.

It can be hard to tell constitutional delay from permanent GnRH deficiency at first. Sometimes the answer becomes clear only with time.

Treatment

• Watchful waiting: for constitutional delay, if the teen is comfortable with it, with checks every 4 to 6 months.
• Short-course sex hormones: low-dose testosterone for boys or low-dose estrogen for girls, typically for 3 to 6 months, to start puberty and the growth spurt. This does not reduce adult height and often prompts the teen's own puberty to start.
• Long-term hormone replacement: for permanent hypogonadism, increasing the dose gradually to mimic natural puberty. Girls later add progesterone to have periods.
• Treating the cause: nutrition and weight restoration, a gluten-free diet for celiac disease, thyroid hormone, medicines for prolactinomas, or surgery for tumors.
• Fertility: people with hypogonadotropic hypogonadism can often have fertility treatment with gonadotropin injections later in life.
• Emotional support: counseling, and practical help with school and sport.

Frequently asked questions

What age is considered delayed puberty?

Puberty is considered delayed if a girl has no breast development by age 13, or a boy has no testicular enlargement by age 14. It is also a concern if a girl has no period by 15, or if puberty starts but does not progress normally over several years.

What is the most common cause of delayed puberty?

The most common cause is constitutional delay of growth and puberty, a normal variation in which a healthy child develops later than peers, often like a parent did. It is especially common in boys. These teens catch up and usually reach a normal adult height.

Is delayed puberty in boys normal?

Many boys with delayed puberty are healthy late bloomers, and constitutional delay is far more common in boys than girls. However, boys should still be checked by a doctor at age 14 if there are no signs of puberty, to exclude hormone, genetic or chronic illness causes.

Can delayed puberty affect height?

Children with constitutional delay usually reach a normal adult height for their family, though some end up slightly shorter than predicted. Untreated permanent hormone deficiency can lead to long limbs and weak bones. Some causes, such as Turner syndrome, affect height themselves.

Can exercise or dieting delay puberty?

Yes. Intensive training and restricted eating can leave the body with too little energy, which switches off puberty hormones. This is common in gymnasts, dancers and distance runners, and in eating disorders. Puberty usually resumes once energy intake matches training and weight is restored.