The causes of early puberty in girls
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Dr Sarah Temple
A family doctor with more than 20 years experience working with children in both General Practice and Mental Health Services. Trained to run Emotion Coaching Parenting Courses. She has a special interest in the link between child and parental wellbeing.
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The causes of early puberty in girls

Girls in developed countries are increasingly facing early puberty. It is especially prevalent amongst some ethnic groups, such as African-American girls in the USA. Early puberty is not just emotionally challenging, it also can also have implication for a girl's growth and development as early puberty can stunt final adult height. There are several probable underlying causes of early puberty in girls in developed countries as well as early adrenarche.
In Short
A girl's percentage fat deposit is the main driver of puberty onset. Increased food portions and childhood obesity is one of the main drivers of early puberty.

Around 100 years ago the age of girls at their first period was around 16 years old in the UK. With improved nutrition, age at first period had dropped to 13 years by the 1940s. Now the age of first menstruation is STILL 13 years, but breast development has got earlier and earlier.

In the last century, the time from initial breast development to the first period was 18 months.  This has now increased to 3 years, so puberty is lasting much longer than in the past.

Causes of early puberty in girls

Doctors and epidemiologists have reported several factors that associated with earlier puberty. These include:

  • Increased fat deposits.
  • Ethnic group.
  • Formula feeding as a baby.
  • Early weaning onto solid food.
  • Stress.
  • ‘Stepfather effect’ – see below.
Fat levels and obesity

At the turn of the twentieth century, the age of girls at their first period was 16 years old in the UK. With improved nutrition this age had dropped to 13 years by the 1940s. Interestingly, the age of first menstruation is still 13, but breast development has got earlier and earlier since the end of the Second World War in the UK and USA.

In the past, the time from initial breast development to the first period was 18 months. This has now increased to 3 years, so puberty is lasting much longer than in the past.

The main factor that leads to earlier onset of puberty (usually marked by the beginning of breast development) is percentage body fat. In the USA today, one-fifth of girls are overweight, and breast development is commonly seen from 9 years old now.

There has been a rapid increase in obesity rates in all developed countries, in the UK 7 percent of children aged six to 11 were obese in 1980, nearly 18 percent were obese in 2012.

Race differences in onset of puberty

In the early 1990’s studies of American girls reported that breast development began on average at 8.87 years in African-Americans and 9.96 years in white girls with similar findings in Europe.

In 2013 the USA data reported that breast development had started by seven years in:

  • 23 % of African American girls.
  • 15 % of Hispanic girls.
  • 10 % of white girls.
Formula feeding as a baby

A 2015 study that tracked some 1,200 girls and their mothers’ breastfeeding habits found that breastfeeding and length of time a girl was breastfed correlated with later breast development in girls in some populations. This means that breastfeeding girls may offer a protective effect against early puberty.

Early stress

Stress seems to bring on puberty earlier too with girls who experience chronic stress, e.g., girls raised in Romanian orphanages, going into puberty early.

The Stepfather Effect

There is also a so-called ‘Stepfather Effect’ and absent father effect on age of onset of puberty. Researchers have found that girls that live in a house with an adult man, e.g., a stepfather, that isn’t biologically related to them, are more likely to experience an earlier onset of puberty. Endocrinologists have speculated that there may be a pheromonal effect, either that unrelated adult males produce a chemical that promotes puberty or perhaps that related males (biological fathers) who live in the home with their daughters may produce a chemical that helps to suppress their puberty. These pheromonal effects have been found in other mammal species, e.g., meerkats and banded mongooses.

The risks to girls who go through early puberty

Girls who experience early puberty are at risk of a range of psychological and social difficulties. This stems from the fact that their physical development is years ahead of their emotional development.

When girls appear more physically developed, adults assume they also have a similarly advanced emotional development but the two are not linked. This leads to children being treated like adults.

Professor Jeanne Brooks-Gunn, a child development expert at Columbia University in the USA has reported the following risks in girls who experience early puberty compared to girls who enter puberty later than average:

  • Increased self-consciousness.
  • Negative body image.
  • Increased depressive symptoms.
  • Three times more likely to have an eating disorder.
  • Twice as likely to take drugs.
  • Twice as likely to attempt suicide.
Adrenarche and body hair production

Not all changes in adolescence are mediated by sex hormones, the adrenal glands also drive ‘adrenarche’.

Adrenarche is an early sexual maturation stage in some higher primates. In humans it typically occurs at around 10-11 years. During adrenarche the adrenal cortex (part of the adrenal gland above the kidneys) secretes increased levels of androgens.

Underarm hair and pubic hair is mediated by androgens from the adrenal glands that sit on top of the kidneys. This adrenal system or adrenarche also promotes the development of sweat production, increased skin sebum production and acne.

As puberty progresses in teenage girls, the ovaries themselves become the main site of androgens production (which is converted into testosterone).

However, if your daughter was born ‘small for dates’ because of intrauterine growth restriction, they may enter start developing body hair before breast development begins.

Early adrenarche

Some girls enter premature adrenarche and develop pubic hair, underarm hair, oily skin and increased perspiration in middle childhood. This can also be coupled with increased mood swings and may not be timed with breast development.

What can be done to protect girls from early puberty?

Nutrition and weight gain seem to be the biggest risk factor in early puberty. Looking at the data, it seems that exclusive and extended breastfeeding of a baby girl may delay the onset of puberty later in life. Throughout a girl’s life lots of physical activity and a balanced diet with help to prevent childhood obesity.

Extrapolating from link between extreme chronic and toxic stress in infancy (experienced by children in Romanian orphanages at the end of the Twentieth Century) and early puberty, it would seem that reducing or removing chronic stress will help to protect girls from early puberty as well as other risk factors such as future mental health problems and addictions. The most fundamental source of protection from chronic stress is a loving bond with a sensitive and available parent. For more information read our article about the affect of good attachment on emotional development in children.

Treatment for early puberty

There is treatment available for girls who experience very early puberty. This involves hormonal treatment to reverse puberty. This can protect bone maturity and reduce breast development. The former can help to maximise final height as girls who have early puberty may end up with a lower final height as the growth plates on the leg bones fuse after puberty which means they can miss out on a growth spurt if they have had an early puberty.

When children go into andrenarche or puberty early they can be offered hormone therapy too.

References and further reading

Julianna Deardorff PhD & Louise Greenspan MD (2014) ‘The New Puberty: How to Navigate Early Development in Today’s Girls.’ Rodalle Books

Graber, J. A., Nichols, T. R., & Brooks-Gunn, J. (2010). Putting pubertal timing in developmental context: Implications for prevention. Developmental Psychobiology, 52, 254–262.

Lynne, S. D., Graber, J. A., Nichols, T. R., Brooks-Gunn, J., & Botvin, G. J. (2007). Links between pubertal timing, peer influences, and externalizing behaviors among urban students followed through middle school. Journal of Adolescent Health, 40, 181e7-181e13.

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This article is for information only and should not be used for the diagnosis or treatment of medical conditions. Essential Parent has used all reasonable care in compiling the information from leading experts and institutions but makes no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details click here.