title: Genetic influences on hormonal markers of chronic hypothalamic-pituitary-adrenal function in human hair.
abstract: BACKGROUND
  Cortisol is the primary output of the hypothalamic-pituitary-adrenal (HPA) axis and is central to the biological stress response, with wide-ranging effects on psychiatric health. Despite well-studied biological pathways of glucocorticoid function, little attention has been paid to the role of genetic variation. Conventional salivary, urinary and serum measures are strongly influenced by diurnal variation and transient reactivity. Recently developed technology can be used to measure cortisol accumulation over several months in hair, thus indexing chronic HPA function.
  
  
  METHODS
  In a socio-economically diverse sample of 1070 twins/multiples (ages 7.80-19.47 years) from the Texas Twin Project, we estimated effects of sex, age and socio-economic status (SES) on hair concentrations of cortisol and its inactive metabolite, cortisone, along with their interactions with genetic and environmental factors. This is the first genetic study of hair neuroendocrine concentrations and the largest twin study of neuroendocrine concentrations in any tissue type.
  
  
  RESULTS
  Glucocorticoid concentrations increased with age for females, but not males. Genetic factors accounted for approximately half of the variation in cortisol and cortisone. Shared environmental effects dissipated over adolescence. Higher SES was related to shallower increases in cortisol with age. SES was unrelated to cortisone, and did not significantly moderate genetic effects on either cortisol or cortisone.
  
  
  CONCLUSIONS
  Genetic factors account for sizable proportions of glucocorticoid variation across the entire age range examined, whereas shared environmental influences are modest, and only apparent at earlier ages. Chronic glucocorticoid output appears to be more consistently related to biological sex, age and genotype than to experiential factors that cluster within nuclear families.
authors.affiliation: Department of Psychology, University of Texas at Austin, Austin, TX,USA.|Population Research Center, University of Texas at Austin, Austin, TX,USA.
authors.forename: E M
authors.initials: EM
authors.lastname: Tucker-Drob
authors.affiliation: Department of Psychology, University of Texas at Austin, Austin, TX,USA.
authors.forename: A D
authors.initials: AD
authors.lastname: Grotzinger
authors.affiliation: Department of Psychology, University of Illinois at Urbana-Champaign, Champaign, IL, USA.
authors.forename: D A
authors.initials: DA
authors.lastname: Briley
authors.affiliation: Department of Psychology, University of Texas at Austin, Austin, TX,USA.
authors.forename: L E
authors.initials: LE
authors.lastname: Engelhardt
authors.affiliation: Department of Psychology, University of Texas at Austin, Austin, TX,USA.
authors.forename: F D
authors.initials: FD
authors.lastname: Mann
authors.affiliation: Department of Psychology, University of Texas at Austin, Austin, TX,USA.
authors.forename: M
authors.initials: M
authors.lastname: Patterson
authors.affiliation: Department of Biological Psychology, Technische Universität Dresden, Dresden,Germany.
authors.forename: C
authors.initials: C
authors.lastname: Kirschbaum
authors.affiliation: Deparment of Human Development and Social Policy, Northwestern University, Evanston, IL, USA.
authors.forename: E K
authors.initials: EK
authors.lastname: Adam
authors.affiliation: Department of Psychology, University of Texas at Austin, Austin, TX,USA.
authors.forename: J A
authors.initials: JA
authors.lastname: Church
authors.affiliation: Department of Psychology, Northwestern University, Evanston, IL, USA.
authors.forename: J L
authors.initials: JL
authors.lastname: Tackett
authors.affiliation: Department of Psychology, University of Texas at Austin, Austin, TX,USA.|Population Research Center, University of Texas at Austin, Austin, TX,USA.
authors.forename: K P
authors.initials: KP
authors.lastname: Harden
keywords: Cortisol; gene–age interaction; hair hormones; hypothalamic–pituitary–adrenal axis; quantitative genetics