Precocious and Early Onset Puberty

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Puberty is a normal transitional stage of adolescence during which the body matures into its adult form. Puberty is not a disease or a disorder of the reproductive system; however, in some cases, puberty may begin early, called early puberty, or extremely early, known as precocious puberty. Precocious or early onset puberty can present daunting challenges and create a lot of stress for both girls and their families. These complex health conditions are neither the fault of the girls or their families. Typically, girls begin the process of puberty, or the beginnings of maturity, any time between the ages of eight to thirteen. In medical settings, the guidelines for rating the development of puberty are called Tanner Staging or Sexual Maturity Rating (SMR). Tanner Stages were first outlined by W. A. Marshall and J. M. Tanner, M.D., in 1969. Tanner Stage 1 is pre-puberty and Stage 5 represents the development of the adult form.

The Basics of Puberty

Puberty involves the endocrine system—the system in the body through which hormones send messages. It starts with an increase of hormones in the body. The process begins with an increase of a hormone called Gonadotropin Releasing Hormone (GnRH). GnRH is released by a structure in the brain called the hypothalamus, which sits at the base of the brain and controls hormone release from other parts of the body. The release of GnRH triggers the release of luteinizing hormone (LH) and follicle stimulating hormone (FSH), and these go on to tell the ovaries to begin producing estrogen and progesterone in girls and testosterone in boys. Estrogen and progesterone are female sex hormones that help regulate the female reproductive system. Estrogen is made in the ovaries and fat cells, while progesterone is produced in the ovaries and the brain. 

As explained by Mickey Emmanuel, M.D., and Brooke Bokor, M.D., Tanner Stage 2 has begun when the body starts developing physical changes in response to these hormones. This stage begins on average at 10 years old in white girls and at 8.9 years old in Black girls. Tanner Stage 2 begins with breast buds and downy pubic hair. Stage 3 is marked by breast development and the growth of coarse pubic hair. The menstrual cycle, or menses, begins at Tanner Stage 3, accompanied by further breast and pubic hair development. Tanner Stage 4 brings about even more breast development and a greater distribution of pubic hair, and Stage 5 is the full adult expression of the body and usually comes sometime after age 15. 

Talking to Your Child About Puberty

Many of us grew up with parents or caregivers who felt uncomfortable talking about topics surrounding puberty and menstruation. Having said that, we recognize that they themselves were possibly raised in homes where these topics were seen as taboo or secretive. Based on this, it may initially feel awkward to have ongoing conversations with your child about this subject. However, learning more about puberty can help prepare you to engage with and answer questions from your child about the changes that will occur physically and mentally during that process. Consider having multiple conversations about puberty and what they will experience throughout their childhood in order for them to learn about these changes over time instead of having “the talk” once. There are a variety of resources available and tips on how to talk to your child about puberty and early puberty. 

If your child has begun menstruation or puberty before you have had the chance to have these discussions—make sure to begin to have age-appropriate conversations. Experiencing changes to the body without prior knowledge can be frightening, so emphasize that this is a natural process that all bodies go through as they develop, and these changes occur at different times for different individuals. Make sure to also discuss menstrual hygiene options such as pads, tampons, and menstrual cups if your child is at the appropriate age.

What Defines Early-Onset and Precocious Puberty?

Early puberty is characterized by any signs of pubertal development occurring between the ages of eight and nine. Girls may see bodily changes such as the development of breasts and pubic hair, and in some cases they may experience their first period. One of the first signs of early onset puberty is often a growth spurt. Precocious puberty is characterized by the same signs as early puberty; the key difference, according to the Mayo Clinic, is that these signs, including menstruation, appear before the age of eight. However, signs of Tanner Stage 2 can appear in girls as young as four years old. Precocious puberty is more prevalent in girls, and it affects about 1% of the U.S. population. 

Medical and public health researchers who have been studying the development of puberty in girls have concluded that in the United States, girls are starting puberty at younger ages. Research conducted by John Robertson in 1818 shows that Black and white girls experienced puberty at the same age in the past, so scientists know that there is no genetic difference dictating this change. This pattern of earlier and earlier puberty has been noted as far back as the early 1920s and continues to accelerate, especially over the past 50 years. This early development disproportionately affects Black girls. A landmark research study in 1997 led by Marcia E. Herman-Giddens, P.A, M.P.H., Dr.PH, et al. found that by age eight, 48% of Black girls showed signs of early onset puberty while only 15% of their white counterparts were affected. The study goes on to show that 23 to 40% of Black girls between the ages of seven and eight are already experiencing the early onset of puberty, as measured through breast and pubic hair development as well as early menstrual periods. 

Similarly, a 2010 study by Frank M. Biro, M.D., et al. measured signs of breast development at both ages seven and eight in a group of girls from different ethnicities. Their findings showed that by age seven, 10.4% of white girls and 23.4% of Black girls showed signs of breast development, or Tanner Stage 2. By age eight, 42.9% of Black girls were showing signs of breast development compared to only 18.3% of white girls. 

What Are Some Causes of Precocious and Early Puberty?

There is a growing body of evidence-based research that links the early onset of puberty to factors including a lack of physical activity, childhood obesity, highly-processed foods, and exposure to environmental toxic chemicals. Genetics can also cause early onset puberty, but these cases are relatively rare.

A Lack of Physical Activity
According to research conducted by Dr. Magda
Vandeloo et al., a lack of physical activity is associated with an earlier age of menstruation. While it is important for children to be physically active, access to physical activity is not equitable. Many social determinant factors, such as socioeconomic status, where people live, and access to safe outdoor recreational spaces, can make it difficult for parents and caregivers to ensure children get adequate exercise.

Obesity and Highly-Processed Foods
According to Paul Kaplowitz, M.D., Ph.D., et al., being overweight or obese plays a role in the development of precocious or early puberty. This is likely because estrogen is released by fat cells as well as the ovaries. The more fat cells that are in the body, the more estrogen may be released. Excess amounts of estrogen and progesterone in the body may confuse the brain into thinking that puberty is ready to begin when it might not be. Body mass index (BMI) is often used as a measurement of whether a person is under- or overweight or falling within a normalized range. BMI is defined by the CDC as a person’s weight in pounds divided by their height in inches squared. An individual is considered overweight with a BMI over 25 and obese with a BMI greater than 30. However, BMI does not take into account a person’s muscle mass or bone density; therefore, it is not a precise measurement of health. 

Research shows that Black children are at a higher risk of obesity than white children. This may be one of the reasons Black girls are disproportionately affected by precocious or early onset puberty. According to a 2018 study by Inyang A. Isong, M.D., M.P.H., et al., 20.8% of non-Hispanic Black children experience childhood obesity compared to 15.9% of white children. Aside from the potential for experiencing puberty early, excessive weight can add to or cause a myriad of other health problems.

In his book Fat Chance, Robert H. Lustig, M.D., writes about studies conducted across different ethnicities. He explains the connection between obesity and early onset of puberty in girls. Dr. Lustig also talks about chemicals called obesogens that promote fat storage into existing cells increasing the chances of weight gain and obesity. Weight gain can also result from consuming highly-processed foods. These foods tend to include high amounts of added sugar and fat to help the food taste better and increase shelf life. Almost 80% of food items sold in the United States contain added sugar. The prevalence and easy availability of these foods make them difficult to avoid, as does the direct marketing of processed foods to children. In addition, a lack of access to and the high costs of fresh, healthy foods are among some of the major challenges parents and caregivers face in feeding their families. Yet another factor compounding the problem, many parents and caregivers work multiple jobs, which can make it difficult to find time to prepare healthy, home-cooked meals.

Exposure to Toxic Chemicals

Toxic chemical exposure may also lead to an earlier onset of puberty because many toxic chemicals are endocrine-disrupting chemicals (EDCs). According to a series of interviews that RSP conducted with Tamarra James-Todd, M.P.H., Ph.D, of the Harvard School of Public Health, EDCs are any chemicals that affect the endocrine system. Some of these chemicals are structurally similar to estrogen, and therefore recognized by the body as estrogen. This fools the body into thinking puberty-related hormones are being released, and this estrogenic effect can trigger puberty at a young age. Several pesticides are also classified as EDCs, which makes it important to keep organic foods in mind. Unfortunately, these chemicals are commonplace and widespread, including in personal care products, and exposure can start in the womb.

It is important to recognize that parents and caregivers may not be aware of the chemicals they and their children are exposed to on a regular basis. The government’s regulatory bodies have not done enough to identify and restrict the use of these chemicals or require proper labeling to inform consumers of the risks to their health. The Food and Drug Administration (FDA), which is responsible for the regulation of personal care products, does not have to approve a product before it goes to market. It does not test them, but rather it relies on the companies that produce these items to do their own safety tests.

What Are Some Common Classes of EDCS?

  • Bisphenols – Bisphenols, such as Bisphenol A (BPA), make plastics tougher and clearer. These can be found in plastic bottles, pacifiers, and canned food.
  • Phthalates – Phthalates make plastics softer and more flexible and can be found in personal care products like moisturizers, fragrances, and hair spray.
  • PFAS – PFAS help increase resistance to stains, water, oil, and grease. Food packaging, non-stick cookware, and water repellents can all be sources of PFAS.
  • Parabens – Parabens act as preservatives in personal care products like conditioners, shampoos, and makeup.
  • Triclosan – This chemical is designed to kill dangerous microorganisms. Furniture, clothing, mouthwash, and toys can all contain triclosan.

Where Can EDCs Be Found In Our Daily Lives?

These chemicals are ubiquitous and can be found in our work and home environments, common household and personal care products, furniture, clothing, and so much more. People may be exposed to EDCs daily by:  

  • Residing in older homes or using older household items. Being around some second-hand furniture, clothing, and home products prior to chemical regulations can be hazardous as these items can create harmful household dust. When dust forms in the home, these particles may be ingested, inhaled, or absorbed through the skin. Even newer items, made after these regulations, may contain dangerous chemicals because since the Toxic Substances Control Act was passed in 1976, only about 200 of 84,000 chemicals have been tested by the Environmental Protection Agency.
  • Using plastic items such as food storage containers, baby bottles, and even toys. BPA has been recognized as a dangerous chemical and has been phased out of many products, but a 2017 study by Dr. Robin Mesnage et al. shows that though companies may replace BPA in BPA-free plastics, the replacements are often bisphenol variants that can have estrogenic effects as well. Some of these additives are just as harmful as BPA—like Bisphenol F (BPF) and Bisphenol B (BPB). These are regrettable substitutions for BPA. In addition, many of the toys that children play with are made of plastic, some of which contain EDCs. In the U.S., EDCs in toys are beginning to be regulated and banned, but many toys made in other countries are still being made with plastic containing these toxic chemicals. It is difficult if not impossible to know which plastic products are safe to use because they are unregulated and companies often keep the chemical makeup of their plastics a secret.
  • Using hair care and highly-fragranced products. One reason Black girls are disproportionately affected by early onset puberty may be because they use different hair products than their non-Black counterparts. Some hair and personal care products are especially harmful. In a 2018 research study by Silent Spring Institute, 18 hair products marketed to Black women were tested and all were found to contain potentially dangerous chemicals. Particularly worrisome are the hair relaxers that are marketed towards children; these contain “the highest levels of 5 chemicals prohibited in the EU or regulated in the US.” Studies have shown an association between hair oil usage and an earlier age of menstruation, with the length of time and the frequency of use influencing when early puberty begins. Many products list “fragrance” as an ingredient in their personal care products, but it is impossible to tell what combination of chemicals are included in the fragrance. In addition, some companies market their products as “green” or “natural,” but they may still contain dangerous chemicals.
  • Consuming harmful chemicals that are found in highly-processed foods and fast food. A 2021 study led by Lariah Edwards, Ph.D, et al. found levels of phthalates in hamburgers, chicken nuggets, fries, chicken burritos, and cheese pizzas from various fast-food restaurants. Sources of these chemicals may include chemical food additives to increase shelf life and improve taste. A 2021 study conducted by Katherine S. Carlos, Ph.D., et al. found phthalates in fast-food packaging as well, especially in cardboard boxes. These chemicals can leach into the food, adding to the levels of EDCs already present in processed foods. Fresh foods that are not organic, including fruits and vegetables, can also be sources of chemical exposure as they are often sprayed with pesticides, which are major sources of EDCs.

For more on EDCs, see our interview with Dr. Tamarra James-Todd on endocrine disrupting chemicals below.

More about Precocious + Early Puberty

Glossary + Resources

Early Onset and Precocious Puberty with Dr. Tamarra James-Todd