While the connection has been well established between obesity and precocious puberty in girls, a Chilean study presented at ENDO 2019 establishes a link between obesity and precocious puberty in boys.
According to statistics from Pediatric Obesity—Assessment, Treatment, and Prevention: An Endocrine Society Clinical Practice Guideline as well as Endocrine Facts and Figures: Obesity, the pediatric obesity epidemic continues to be a global health threat. In the U.S., pediatric obesity affects 16.9% of children and adolescents, while another 31.8% meet the criteria for overweight, with the multitude of associated risks for long-term health complications and comorbidities looming in adulthood.
In addition to the health problems it may cause, pediatric obesity also seems to disrupt the endocrine system in multiple ways. One such disruption is seen with precocious puberty in girls. Until now, evidence suggesting that pediatric obesity also initiates early puberty in boys has been conflicting, with some studies showing a correlation only with overweight status and some finding that pediatric obesity actually delays puberty. A new study, however, may just settle the controversy.
Blooming Too Early
In research presented at ENDO 2019, Verónica Mericq, MD, from the Universidad De Chile in Santiago, and team demonstrate an association of both central and total adiposity with earlier pubertal events in boys. Their longitudinal follow-up study included 527 Chilean boys who were participants in the Growth and Obesity Chilean Study (GOCS) starting at age four. After weight, height, and waist circumference were measured and body mass index (BMI) calculated, testicular volume was evaluated starting at around age seven with a Prader orchidometer.
They define obesity as 2 standard deviation scores (SDS) greater than BMI, which equates to the U.S. definition — equal to or greater than the 95th percentile (of the 2000 Centers for Disease Control sex-specific BMI-for-age growth charts). They define precocious gonadarche in boys as a testicular volume greater than 3 ml before nine years of age in either testicle and precocious pubarche as the appearance of pubic hair before age nine, based on the Tanner scale. The defined age at gonadarche and pubarche onset as happening midway between two consecutive visits. The association between obesity and precocious puberty was analyzed through a logistic regression model, with the odds ratio and confidence interval corresponding to 95%.
The team found a positive and statistically significant association between total body obesity and precocious puberty from four to seven years of age, with 45 boys (9.1%) starting puberty early. Compared to boys with healthy weights, boys with obesity had a 2.7 times higher risk of early-onset puberty. They also analyzed BMI as a continuous variable, and the association held up, as it did for central obesity and precocious puberty. For central obesity, which is a more reliable indicator of increased fat mass, the risk was 6.4 times higher. The rates of both central and total adiposity increased among the boys during the study period, from 22% to 28.6% and 11.8% to 17.4%, respectively.
“The underlying mechanisms are not yet fully understood, and whether earlier onset of puberty is based on the activation of the hypothalamic–pituitary–gonadal axis is unclear,” Mericq says. “The most promising link between obesity and puberty is the adipokine–leptin–insulin and its interaction with the kisspeptin system, which is an important regulator of puberty. However, peripheral action of adipose tissue (e.g., via other adipokines, aromatase activity) could also be involved in changes to the onset of puberty.”
As prior studies have shown, other potential mediators linking the onset of puberty to obesity include nutritional factors, epigenetics, and endocrine-disrupting chemicals, she explained. Toxic environmental stress has also been implicated.
Double Jeopardy
So, in addition to the physical burden and health risks that pediatric obesity confers as already described, these children are also at risk for a host of the physical, psychological, social, and emotional problems associated with precocious puberty itself.
On the physical side, precocious puberty has been correlated with type 2 diabetes and adult-onset asthma. The bones of these children stop growing earlier because such growth ceases toward the end of puberty, meaning they may have shorter stature than expected. Their physical childhood is cut short because their bodies show evidence of physical maturity, which can likewise make them vulnerable to bullying and lead to depression, substance abuse, and having sex earlier, consequences possibly related to the stress of being a so-called “early-bloomer” and not being on the same development wavelength as peers. “Early puberty might increase the risk of risk-behavior problems,” said Mericq. For these children, their bodies have physically matured before their brains are ready to process this metamorphosis.
“In addition, it has been postulated that precocious puberty in boys could be related to higher incidence of testicular cancer in adulthood,” she says. This parallels the purported higher risk of breast cancer that girls experiencing early puberty face.
Boys Will Be Boys
Obesity continues to confound researchers and clinicians alike. Although no one fully understands this many-headed hydra and how its pervasive injury to body systems unfolds, experts believe that prevention is the key to battling it. Once it has already occurred, reversing it in a long-lasting way is exceedingly difficult. “Our results suggest that controlling the obesity epidemic could be useful in decreasing the risk for early puberty,” said Mericq. Preventing pediatric obesity can be largely achieved by promoting a healthy diet and encouraging regular activity, according to Pediatric Obesity—Assessment, Treatment, and Prevention: An Endocrine Society Clinical Practice Guideline.
Maintaining a healthy weight might just let boys be boys.
— Horvath is a freelance writer based in Baltimore, Md., and a frequent contributor to Endocrine News.
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