Earlier onset of puberty linked to obesity

Children, especially girls, who are heavier at 5 years of age tend to have lower levels of a protein that affects the onset of puberty and enter puberty earlier than children who weigh less, a new study reports.

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Levels of the protein-sex hormone-binding globulin (SHBG), which binds to androgen and estrogen-are normally high during childhood but fall markedly before puberty, paving the way for puberty to happen.

When researchers examined annual longitudinal physiologic and endocrine data on 347 children, aged 5 to 15 years, in the United Kingdom, they found that the heavier children, especially the girls, tended to have lower levels of SHBG throughout childhood and start puberty earlier than their lower-weight peers. Data showed SHBG levels were highest at 5 years and mean levels were higher in boys than girls. By 15 years, mean levels were lower in boys than girls.  

Statistical analysis revealed that 5 covariates related to adiposity (body mass index standard deviation scores, or BMIsds)-insulin, leptin, adiponectin, insulin-like growth factor (IGF-1), and C-reactive protein (CRP)-significantly affected SHBG levels. Adding BMIsds to the mix erased the significance of leptin, insulin, and adiponectin, but not CRP and IGF-1. In other models, BMIsds displaced the individual effects on SHBG of insulin, leptin, IGF-1, and adiponectin, but not CRP.

Based on their findings, the researchers propose that adiposity integrates the effects of individual hormonal signals to lower SHBG and, along with low-grade inflammation, may help account for the connection between increasing weight and earlier age of puberty. They suggest that the findings may shed light on the declining age of puberty around the world in recent decades as obesity increases. 

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