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1 Pediatric Endocrine Unit, MassGeneral Hospital for Children and Harvard Medical School, Boston, Massachusetts, United States
2 Radiology, Massachusetts General Hospital, Boston, Massachusetts, United States
3 Neuroendocrine Unit, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, United States
* To whom correspondence should be addressed. E-mail: mmisra{at}partners.org.
Background: Although overweight adolescents have markedly altered body composition, insulin sensitivity and lipids, hormonal associations with these parameters have not been well characterized. Growth hormone (GH) deficiency and hypercortisolemia predispose to abdominal adiposity and insulin resistance, and GH secretion is decreased in obese adults. Objective: We hypothesized that low peak GH on the GHRH-arginine stimulation test, and high cortisol in overweight adolescents would be associated with higher regional fat, insulin resistance and lipids. Design/Methods: We examined the following in 15 overweight girls and 15 bone-age-matched controls 12-18 years: (i) body composition using DXA and MR [visceral and subcutaneous adipose tissue (VAT and SAT) at L 4-5, and soleus-intramyocellular lipid (IMCL) (1H-MRS)], (ii) peak GH on the GHRH-arginine stimulation test, (iii) mean overnight GH and cortisol, (iv) 24-hour urine free cortisol (UFC), (v) fasting lipids, and (vi) an OGTT. Stepwise regression was the major tool employed to determine relationships between measured parameters. Results: Log peak GH on the GHRH-arginine test was lower (p=0.03) and log UFC higher (p=0.02) in overweight girls. Log mean cortisol (overnight sampling) was associated positively with SAT, and with BMI-SDS accounted for 92% of its variability, whereas log peak GH and BMI-SDS accounted for 88% of VAT variability, and log peak GH for 34% of the IMCL variability. Log mean cortisol was independently associated with log HOMA-IR, LDL and HDL and explained 49- 59% of the variability. Conclusions: Lower peak GH and higher UFC in overweight girls are associated with visceral adiposity, insulin resistance and lipids.
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