title: In Obesity, HPA Axis Activity Does Not Increase with BMI, but Declines with Aging: A Meta-Analysis of Clinical Studies.
abstract: BACKGROUND
  Obesity is one of the major public health challenges worldwide. It involves numerous endocrine disorders as etiological factors or as complications. Previous studies strongly suggested the involvement of the hypothalamic-pituitary-adrenal (HPA) axis activity in obesity, however, to date, no consistent trend in obesity-associated alterations of the HPA axis has been identified. Aging has been demonstrated to aggravate obesity and to induce abnormalities of the HPA axis. Thus, the question arises whether obesity is correlated with peripheral indicators of HPA function in adult populations.
  
  
  OBJECTIVE
  We aimed to meta-analyze literature data on peripheral cortisol levels as indicators of HPA activity in obesity during aging, in order to identify possible explanations for previous contradictory findings and to suggest new approaches for future clinical studies.
  
  
  METHODS
  3,596 records were identified through searching of PubMed, Embase and Cochrane Library Database. Altogether 26 articles were suitable for analyses.
  
  
  METHODS
  Empirical research papers were eligible provided that they reported data of healthy adult individuals, included body mass index (BMI) and measured at least one relevant peripheral cortisol parameter (i.e., either morning blood cortisol or 24-h urinary free cortisol).
  
  
  METHODS
  We used random effect models in each of the meta-analyses calculating with the DerSimonian and Laird weighting methods. I-squared indicator and Q test were performed to assess heterogeneity. Meta-regression was applied to explore the effect of BMI and age on morning blood and urinary free cortisol levels. To assess publication bias Egger's test was used.
  
  
  RESULTS
  Obesity did not show any correlation with the studied peripheral cortisol values. On the other hand, peripheral cortisol levels declined with aging within the obese, but not in the non-obese groups.
  
  
  CONCLUSIONS
  Our analysis demonstrated that obesity or healthy aging does not lead to enhanced HPA axis activity, peripheral cortisol levels rather decline with aging.
authors.affiliation: Institute for Translational Medicine, Medical School, University of Pécs, Pécs, Hungary.
authors.forename: Judit
authors.initials: J
authors.lastname: Tenk
authors.affiliation: Institute for Translational Medicine, Medical School, University of Pécs, Pécs, Hungary.|Institute of Bioanalysis, Medical School, University of Pécs, Pécs, Hungary.
authors.forename: Péter
authors.initials: P
authors.lastname: Mátrai
authors.affiliation: Institute for Translational Medicine, Medical School, University of Pécs, Pécs, Hungary.|Department of Translational Medicine, University of Pécs, Pécs, Hungary.|Hungarian Academy of Sciences - University of Szeged, Momentum Gastroenterology Multidisciplinary Research Group, Szeged, Hungary.
authors.forename: Péter
authors.initials: P
authors.lastname: Hegyi
authors.affiliation: Institute for Translational Medicine, Medical School, University of Pécs, Pécs, Hungary.
authors.forename: Ildikó
authors.initials: I
authors.lastname: Rostás
authors.affiliation: Institute for Translational Medicine, Medical School, University of Pécs, Pécs, Hungary.
authors.forename: András
authors.initials: A
authors.lastname: Garami
authors.affiliation: Department of Gastroenterology, First Department of Internal Medicine, University of Pécs, Pécs, Hungary.
authors.forename: Imre
authors.initials: I
authors.lastname: Szabó
authors.affiliation: Institute for Translational Medicine, Medical School, University of Pécs, Pécs, Hungary.
authors.forename: Margit
authors.initials: M
authors.lastname: Solymár
authors.affiliation: Institute for Translational Medicine, Medical School, University of Pécs, Pécs, Hungary.
authors.forename: Erika
authors.initials: E
authors.lastname: Pétervári
authors.affiliation: Department of Gastroenterology, First Department of Internal Medicine, University of Pécs, Pécs, Hungary.
authors.forename: József
authors.initials: J
authors.lastname: Czimmer
authors.affiliation: Institute for Translational Medicine, Medical School, University of Pécs, Pécs, Hungary.|Department of Translational Medicine, University of Pécs, Pécs, Hungary.
authors.forename: Katalin
authors.initials: K
authors.lastname: Márta
authors.affiliation: Institute for Translational Medicine, Medical School, University of Pécs, Pécs, Hungary.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Mikó
authors.affiliation: Institute for Translational Medicine, Medical School, University of Pécs, Pécs, Hungary.
authors.forename: Nóra
authors.initials: N
authors.lastname: Füredi
authors.affiliation: Institute for Translational Medicine, Medical School, University of Pécs, Pécs, Hungary.|Department of Translational Medicine, University of Pécs, Pécs, Hungary.
authors.forename: Andrea
authors.initials: A
authors.lastname: Párniczky
authors.affiliation: Institute for Translational Medicine, Medical School, University of Pécs, Pécs, Hungary.
authors.forename: Csaba
authors.initials: C
authors.lastname: Zsiborás
authors.affiliation: Institute for Translational Medicine, Medical School, University of Pécs, Pécs, Hungary.
authors.forename: Márta
authors.initials: M
authors.lastname: Balaskó
mesh_terms: D000328:Adult; D000375:Aging / Q000502:physiology*; D015992:Body Mass Index; D000068456:Clinical Studies as Topic; D005260:Female; D006801:Humans; D006854:Hydrocortisone / Q000097:blood / Q000378:metabolism* / Q000652:urine; D007030:Hypothalamo-Hypophyseal System / Q000378:metabolism / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000503:physiopathology*; D010913:Pituitary-Adrenal System / Q000378:metabolism / Q000503:physiopathology*; D012044:Regression Analysis; D055815:Young Adult
chemical_list: D006854:Hydrocortisone