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Childhood obesity decreased SHBG, lowered puberty age
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Hormonal disturbances associated with weight gain, along with chronic inflammation, could help explain the declining age of puberty, according to research published in The Journal of Clinical Endocrinology & Metabolism.
“The hormones that control reproduction are intimately linked with the hormones that respond to increasing body weight,” Jonathan Pinkney, MD, of Plymouth University Peninsula Schools of Medicine and Dentistry in the United Kingdom, told Endocrine Today.
The combination of endocrine mechanisms was associated with decreased sex hormone-binding globulin before puberty, and lower levels of SHBG predicted sexual maturity would occur earlier, according to findings in the observational, early bird study.
Jonathan Pinkney
“The study confirms that being overweight as a youngster is associated with earlier and faster puberty,” Pinkney said. “The data we have chosen to present go beyond existing research in humans in identifying a specific set of endocrine mechanisms related to weight gain and obesity that could plausibly explain why earlier puberty occurs in these children.”
Pinkney and colleagues used longitudinal modeling to evaluate annual physiological and endocrine measurements in 347 children aged 5 to 15 years.
SHBG levels were highest at age 5 years and declined thereafter. At age 5 years, mean SHBG levels were higher in boys than girls (difference, 7.68 nmol/L; P=.045). By age 15 years, however, SHGB levels were lower in boys than girls (difference, 12.19 nmol/L; P=.001).
There was an inverse correlation between SHBG and adiposity, insulin, insulin-like growth factor I, C-reactive protein (CRP) and leptin. SHGB correlated positively with adiponectin, but not with dehydroepiandrosterone sulfate, androstenedione or testosterone.
Linear mixed models showed five adiposity-related covariates — insulin, leptin, adiponectin, IGF-I and CRP — significantly affected SHBG. BMI rendered some effects nonsignificant, in these models and others.
Girls with reduced SHBG levels at age 5 years reached pubertal markers earlier; luteinizing hormone secretion, age at peak high velocity and menarche all happened earlier. Boys with reduced SHBG levels at age 5 years also reached pubertal markers earlier; however, no relationships were observed between SHBG and earlier onset of luteinizing hormone secretion or age at peak high velocity.
“This research alone cannot determine whether earlier puberty is in itself a problem for human societies,” Pinkney said. “However, there may be unanticipated social effects of such early maturation, as well as the medical consequences of obesity, although the consequences remain to be fully determined. This would merit further research.” — by Allegra Tiver
Disclosure: The researchers report no relevant financial disclosures.
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