Youthful testimonies

“We must be aware of the fact that it no longer suffices to say that puberty is occurring earlier and earlier. When we observe this trend, we back up our claims with clinical observations", says Professor Bourguignon. This point, which was also addressed in the article "Changes in Pubertal Timing: Past Views, Recast Issues", makes it possible to put into perspective the impact of studies based on self-evaluations by adolescents themselves who were asked to comment on their pubertal development.

Faced with young people who are often reluctant to allow themselves to undergo a physical examination - especially when this is not the reason they came to see the doctor in the first instance – many studies have been based on self-evaluation by adolescents. In order to gather information about young people, different methods have been developed. These are sometimes based on drawings, pictures or on different written propositions. In accordance with the validity of these methods which, it must be remembered, cannot entirely replace examinations by a qualified doctor, contradictory results have sometimes been obtained.

At the University of Liege, a retrospective self-evaluation study asked the respondents the following question: "Between the ages of 8 and 12, boys and girls change physically, but not at the same times. How would you compare your physical development with that of friends of the same age: very precocious, quite precocious, identical, a little later or much later”?
In the answers, many young people felt that they had experienced puberty earlier rather than later. Another study found the same results with 12 to 13% of adolescents admitting to experiencing puberty later than their peers and 28% felt that they had experienced puberty earlier than their friends of the same age. In reality, though two-thirds of the answers concurred with the medical diagnosis, for a large number of young people, things didn’t add up.

This estimation can be explained quite "simply": describing themselves as “early” is more affirming for young people. And yet, detecting the proportion of young people confronted by precocious or later puberty remains an important fact for researchers. In fact, these adolescents are more likely to indulge in risky behaviour…  

The importance of nutrition

Nutrition occupies an important place among the factors involved in the onset of puberty, particularly among girls. Logically, the link between nutrition and puberty has been the subject of many investigations. As the researchers point out, "the energy balance and pubertal timing share common regulatory factors with possible influences during fetal life".

From a theoretical point of view, we know that a sufficient level of adipose mass sends a signal to the neuroendocrine system to initiate puberty by means of leptin (in pubertal maturity, leptin plays a prerequisite role in neuroendocrine control). "Without leptin, puberty is not possible”, explains Professor Bourguignon. “But having leptin does not necessarily trigger puberty". In any case, some authors have suggested obesity as a cause of precocious puberty.

In fact, the availability of energy and adiposity, in tandem with pubertal development, occupies an important role during several stages of life. Recent studies have shown that weight gain linked to variations in nutrition in the first months following birth can have an impact on both puberty and the risk of childhood obesity. Another study revealed that children who have a high body mass index (BMI) at 7 years of age reach puberty quicker. An opposite link was found between weight at birth and the advanced age at which menarche occurs: the lower the weight the earlier puberty arrives. 

On this last point, research conducted on the impact of fetal and/or neonatal dietary restrictions show that the "organism will undergo changes during puberty in different ways according to the different conditions to which it is exposed”, explains Professor Bourguignon. “A deficiency in nutrition that occurs in utero can be interpreted by the organism as a possible threat to the species. This can therefore be interpreted as a necessity to advance the age of pubertal maturity and the ability to reproduce”. On the other hand, malnutrition around the time puberty is approaching can cause exactly the opposite effects. Under adverse conditions, the girl would get pregnant! To avoid such a situation the body thus would program a delay of puberty.
This extraordinary interpretation by the body of the conditions to which a fetus, newly-born or young child or girl is exposed, could also happen in the case of stressful psycho-social situations.

"The concept we are defending is the fact that a simple or simplistic relation cannot be made between nutrition and environment and pubertal timing”, continues Professor Bourguignon. “In fact, everything depends on the moment when the different elements occur. It is precisely these different moments that can be a determining factor”.

Moreover, the authors of the article that appeared in Frontiers of Neuroendocrinology state that the fact remains to be discovered, and this would appear to be the difficulty,  whether there is a continuum between the three periods of sensitivity determined by the researchers  - prenatal, postnatal and childhood, or whether each one acts “separately”.