Understanding Precocious Puberty: Causes & Effects

Precocious puberty is a term that describes the physical and hormonal signs of puberty that may occur at an age younger than is deemed normal.

What’s normal when it comes to puberty?

Puberty is considered to have arrived too early when signs (breast, pubic hair) arrive earlier than 6-8 years of age in girls and before age 9 in boys. Girls with African heritage often see earlier signs than girls of other racial backgrounds.

The benchmark was age 8 for girls, but that had to change since many girls show signs of puberty earlier without it being considered abnormal.

Why hitting puberty too early is bad

Precocious puberty is undesirable for several reasons. An early growth spurt may result in rapid bone development, ending up with a short adult – bone development takes time, so fast-forwarding this process can cause problems. The emotional distress of children in this situation cannot be underestimated either. Seek support.

Signs of precocious puberty in girls

Pubic hair – groin, armpits, body hair (premature pubarche)
Armpit odour
Early menstruation (premature menarche)
Breast development (premature thelarche), may be lopsided
Increased libido
Vulvar changes
Enlarged clitoris or severe acne are abnormal signs of androgen excess and need evaluation
Follicle development in the ovaries
Growth spurt
Boys will see enlarged penis and testicles, body hair, voice changes, and increased libido

The two most common benign, normal variations of precocious puberty are early breast development and early pubic hair development. These are not progressive or are slow to progress.

Premature breast development can be the isolated appearance of breast development, most often in girls under three years of age. Early pubic hair development may appear in boys or girls under the age of seven or eight. A physical examination and health history can determine if true sexual precocity is occurring.

True early puberty needs to be differentiated from what’s known as pseudopuberty. The sorts of precocious puberty are, therefore, split into two categories: central precocious puberty and precocious pseudopuberty.

Central precocious puberty is defined by the presence of hormonal changes that force maturation of in girls the HPO axis – hypothalamic-pituitary-ovarian axis. This triggers physical and hormonal changes that would normally occur in puberty.

Precocious pseudopuberty is far less common, and is defined by increased production of sex hormones, independent of the HPO axis.

Causes of precocious puberty

Children with precocious puberty are almost always otherwise healthy, but the start of the puberty curve starts earlier than the norm. There are sometimes structural abnormalities in the brain found in scans, with a French study finding abnormalities in two per cent of girls who had puberty onset between the ages of six and eight, and in 20 per cent of girls who experienced puberty before the age of six.

A United Kingdom study reported abnormalities in 15 per cent of their study cohort. Amongst those with central precocious puberty, boys are more likely than girls to be found with abnormal scan findings.

Puberty is triggered by the hypothalamus’s gonadotropin-releasing hormone (GnRH), with the suppression of the HPO axis not working adequately.

Abnormalities that allow this process to occur unimpeded include brain tumours, brain injury, abnormal brain growths and congenital abnormalities. Hormones are produced after the signalling system is activated, which causes the sexual maturation of the child, including a growth spurt.

Genes involved in precocious puberty

There is a genetic element to when we hit puberty – a parent or sibling with early puberty may indicate this, as opposed to some issue being present.

Increased BMI in early onset puberty

Increased body mass index (BMI) also adds a risk factor to early puberty, more often in girls, with body weight being one factor in the normal start of menstruation in girls due to the action of aromatase in fat cells.

One study found that an increased BMI at age three and the rate of BMI increase from ages 3-6 were associated with earlier onset of puberty. There seems to be links between BMI and age of onset of puberty, though the reasons remain unclear.

Early pubic hair on its own – what it tells us

If pubic hair appears in the pubic or armpit area without other signs of puberty can be caused by an increase in weak androgens by the adrenal glands.

If other signs of androgen excess appear (enlarged clitoris, growth spurt, severe acne) a tumour should be excluded, as should congenital adrenal hyperplasia. Without any adverse findings, early pubic hair may not be a cause for concern.

Early breast development on its own – what it tells us

Breast development in young girls without other signs of precocious puberty is most often observed in girls under the age of three. Newborns may have breast tissue due to oestrogens in its body from its mother, lasting for more than a year in some babies.

Breast tissue should not really increase much over time, and thickening and pigmentation doesn’t occur as it does in girls with precocious puberty. We’re not sure why this occurs, but small ovarian cysts that produce oestrogen may be responsible. Soy or other sources of phytoestrogens may be responsible in some cases.

Exposure to environmental androgens

Occasionally, children have come into contact with androgens outside of their body, most often adult men who use topical androgens. This can result in genitals enlarging and pubic hair, or other signs of androgens being present. The issue resolves itself when the contact ceases.

Treatment for precocious puberty

Treatment depends entirely on the classification – central precocious puberty is treated quite differently to precocious pseudopuberty. There are four typical medical treatments available:

Do nothing
GnRH analogues – decreases levels of LH and FSH, suppresses puberty promptly
GnRH agonists – suppress pituitary production of gonadotropins, safe and effective
Progestin – synthetic progesterone, Depo-Provera injection, inhibits LH, slows breast growth, stops menses

Outcomes of children with precocious puberty

There is no extra known risk of children who experience early puberty, however any child with an abnormal scan finding has those associated risks attached. There may be an increased risk of breast cancer in girls who experience early puberty.

Emotions and behaviour in puberty

Emotional distress caused by the physical and emotional changes that go with puberty is common. Puberty is strange enough as it is, without adding too young to understand to the list.

Girls who get their period before age nine or ten may withdraw and have difficulties with pads or tampon use. Children may experience libido increases that lead to inappropriate sexual behaviours and increased masturbation.

Girls who experience early puberty are slightly more likely to have earlier sexual activity.

Behavioural problems are common, with less social competency observed compared to peers. Some studies have seen these emotional problems persist into adulthood. Distress can be minimised with proper education and preparation by parents.

Height in precocious puberty

Puberty accelerates growth, so these kids are likely to be taller than everyone else, but result in them being ultimately shorter. Being short is more likely if puberty hits before the age of six. Many will reach heights within the normal range.

Ethnic background involvement in early onset puberty

African American girls were found to have signs of early puberty about one year before Caucasian American girls, but the same has not been found in boys. Mexican-American girls were found to start breast development at about the same time as Caucasian-American girls, with pubic hair appearing slightly later.

Central precocious puberty was found in one study to occur five times more often in girls than boys, with idiopathic central precocious puberty occurring eight times more often. This may be explained by these girls being at the very early end of the normal spectrum.

References^1–3

1.
Chen C, Chen Y, Zhang Y, et al. Association between Dietary Patterns and Precocious Puberty in Children: A Population-Based Study. International Journal of Endocrinology. Published online 2018:1-7. doi:10.1155/2018/4528704
2.
Rohani F, Salehpur S, Saffari F. Etiology of precocious puberty, 10 years study in Endocrine Reserch Centre (Firouzgar), Tehran. Iran J Reprod Med. 2012;10(1):1-6. https://www.ncbi.nlm.nih.gov/pubmed/25242967
3.
Farello G, Altieri C, Cutini M, Pozzobon G, Verrotti A. Review of the Literature on Current Changes in the Timing of Pubertal Development and the Incomplete Forms of Early Puberty. Front Pediatr. Published online May 8, 2019. doi:10.3389/fped.2019.00147