The first signs of puberty are brought forward. Gradually, without major shocks, but the age at which this stage begins is getting younger: today’s girls begin to develop their breasts —thelarche or the appearance of the breast bud, the first sign of puberty— a year earlier than expected. their mothers did, according to An international study published in the journal Jama Pediatrics. The researchers found that thelarche is earlier an average of three months per decade since the end of the seventies of the last century and point to obesity and external endocrine disruptors as the cause of this phenomenon. Menstruation, a sign of the culmination of puberty, also presents a gradual advance, but much less significant, value the voices consulted. Experts warn of long-term health risks if the age of onset of puberty continues to advance.
This stage of transition between childhood and adulthood begins, according to scientific consensus, with the appearance of the first signs of puberty, such as thelarche in girls or testicular growth in boys. They usually start from the age of 10 and they, with the breast button, usually start puberty from the age of nine, explains Raquel Corripio, spokesperson for the Spanish Society of Pediatric Endocrinology: “Between the ages of nine and 13 , 99% of girls show some pubertal change. It is as normal to do it at nine, as at 10 or 11″. Of course, below eight (of nine if they are children), it is considered precocious puberty and requires a medical study to decide if it needs treatment or not.
But when the scientific community speaks of an advance in the beginning of this vital stage, they do not refer to the clinical entity of precocious puberty as such, but to the fact that the transition from childhood to adulthood, although it is still within canons of normality, it starts earlier and earlier, clarifies Manuel Tena, group leader of the Obesity and Nutrition Network Biomedical Research Center (CIBER): “They are not cases of precocious puberty. It is an epidemiological problem: here we are talking about the fact that, from the population point of view, the age of onset of breast development in girls is advanced”.
Anders Juul, author of the study published in Jama Pediatrics and head of the Department of Growth and Reproduction at Rigshospitalet in Copenhagen, recalls that in an article in 2009 they saw this trend: “In Copenhagen we found that the average age of breast development had dropped from 11 years in 1991 to 9.9 years in 2006.” A new scientific review, after analyzing thirty studies, calculates that the age of thelarche decreases at a rate of three months per decade. In menstruation, for its part, although “there is a trend towards an earlier age,” explains Juul, this advance “is less marked compared to the trend of breast development.”
According to Manuel Tena, “a dissociation between the beginning of puberty and the end of it” is being observed. There is a kind of “distortion” in the natural progression of this transitional stage, which used to start with thelarche in girls—sometimes pubic and armpit hair is also added, but not always—and end, around two years later, with the appearance of the first period. “Girls now enter puberty earlier, but don’t menstruate earlier. The space of puberty is widened, there is a widening of the period of pubertal performance”.
In children there is more controversy. An earlier start of puberty is also seen, but it is less studied, admits Corripio: “It would seem that the start of puberty is appearing later in boys. But it is less studied and evidenced because there are fewer cases and it is more difficult to measure the indicator of testicular growth. Boys are considered to start puberty when the testicular size is greater than four milliliters. Tena agrees that there may be underdiagnosis “because the increase in testicular size is difficult to see” and also that greater exposure to estrogenic factors may have a greater effect in boys.
In girls, the experts consulted point to several factors as the cause of this phenomenon. There are no absolute certainties, but everyone agrees that obesity is a key element: There is a correlation between girls with higher body mass index (BMI) and earlier onset of menarche (first period) and thelarche.
A sudden weight gain is enough, clarifies Lourdes Ibáñez, Endocrinology clinical research coordinator at the Sant Joan de Déu Children’s Hospital in Barcelona, to trigger the early onset of puberty. An increase in BMI that represents a change in the percentile from which it came from birth can already generate a response: “We are not talking about being obese. A change in weight of three kilos in a month can already be enough”, explains Ibáñez.
Tena agrees and warns that “a rapid change in weight around puberty can be as decisive as sustained overweight.” One of the keys may be leptin, a hormone that is produced in adipose tissue and acts as a signal to the brain that there are enough energy reserves for the beginning of reproductive age. “In weight gain, there is an increase in leptin levels that indicate to the brain that there is a critical fat mass to start puberty. That is why in very thin girls, leptin is very low and this stage is delayed”.
Juul argues, however, that while heavier girls mature earlier, “other causes are likely to be involved.” And he points to endocrine disruptors, chemicals that are in the environment and mimic hormones within the body. “High levels of phthalates were found to be associated with an early onset of puberty, but no firm general conclusions can be drawn from the human studies,” he says. The review published in Jama Also remember that some chemicals, such as DDT (dichlorodiphenyl-trichloroethane) and DDE (dichlorodiphenyldichloroethylene), have also been associated with earlier puberty.
Experts also point to a third factor that can influence the earlier start of puberty: mental health. Ibáñez warns that the hypothalamus – the part of the brain that secretes the gonadotropin-releasing hormone, key to the development of puberty – “is very sensitive to stress and this can favor the onset of puberty or inhibit ovulation.” Corripio points out, for example, that adoption —but not being a migrant— is a risk factor for premature puberty. Another US study also found an association between exposure to childhood sexual abuse and earlier pubertal onset.
Tena warns that the impact of mental health “is not as well characterized as the role of leptin”, for example, but he does point out that it has also been seen that “in girls from single-parent families, pubertal activation is accelerated”. Juul agrees: “Socioeconomic factors are important. Stress during childhood may play a role: the absence of a father is associated with early puberty in the child.” In daughters of divorced parents, a study also found that menstruation appears earlier, and another investigation with girls from the city of Srebrenicawhere a massacre occurred during the Bosnian war in the 1990s, found that the age of onset of menarche was higher than the control group, who lived in peaceful, unoccupied parts of Bosnia: the researchers concluded that “traumas Psychological disorders, physical injuries and low socioeconomic status, caused by the events of the war, delay the age of menarche.
There are also ethnic differences, Juul points out, such as in the United States, black girls enter puberty earlier than Hispanic and white girls.
The advancement of the age of onset of puberty, in any case, has an impact on health. Juul maintains that “it can cause psychosocial distress and isolation.” “The long-term effects of early puberty include an increased risk of metabolic syndrome and breast cancer,” she notes. A study published in the journal Breast Cancer Research concluded that “mammary duct development may be a time of increased susceptibility to carcinogenesis risk, and greater attention should be paid to the relationship of breast cancer risk with different stages of puberty.”
Tena adds other risks, such as short stature, more cardiovascular and metabolic ailments or gynecological problems. Also more psychological or psychiatric disorders “due to the dissociation between physical and psychological maturation”.
Despite the possible effects on health, experts consider that this phenomenon does not require medical intervention. No, at least, as if it were precocious puberty, for which there is an intramuscular treatment to inhibit the hormones that trigger puberty. “How is it solved? Avoiding all the factors that expose this, such as obesity, ”says Tena.