title: Testosterone trajectories and reference ranges in a large longitudinal sample of male adolescents.
abstract: OBJECTIVE
  Pubertal dynamics plays an important role in physical and psychological development of children and adolescents. We aim to provide reference ranges of plasma testosterone in a large longitudinal sample. Furthermore, we describe a measure of testosterone trajectories during adolescence that can be used in future investigations of development.
  
  
  METHODS
  We carried out longitudinal measurements of plasma testosterone in 2,216 samples obtained from 513 males (9 to 17 years of age) from the Avon Longitudinal Study of Parents and Children. We used integration of a model fitted to each participant's testosterone trajectory to calculate a measure of average exposure to testosterone over adolescence. We pooled these data with corresponding values reported in the literature to provide a reference range of testosterone levels in males between the ages of 6 and 19 years.
  
  
  RESULTS
  The average values of total testosterone in the ALSPAC sample range from 0.82 nmol/L (Standard Deviation [SD]: 0.09) at 9 years of age to 16.5 (SD: 2.65) nmol/L at 17 years of age; these values are congruent with other reports in the literature. The average exposure to testosterone is associated with different features of testosterone trajectories such as Peak Testosterone Change, Age at Peak Testosterone Change, and Testosterone at 17 years of age as well as the timing of the growth spurt during puberty.
  
  
  CONCLUSIONS
  The average exposure to testosterone is a useful measure for future investigations using testosterone trajectories to examine pubertal dynamics.
authors.affiliation: Rotman Research Institute and Institute of Medical Science, University of Toronto, Toronto, Canada.
authors.forename: Ammar
authors.initials: A
authors.lastname: Khairullah
authors.affiliation: Department of Biobehavioral Health and Penn State Institute of the Neurosciences, The Pennsylvania State University, State College, Pennsylvania, United States of America.
authors.forename: Laura Cousino
authors.initials: LC
authors.lastname: Klein
authors.affiliation: School of Social and Community Medicine, University of Bristol, Bristol, United Kingdom.
authors.forename: Suzanne M
authors.initials: SM
authors.lastname: Ingle
authors.affiliation: School of Social and Community Medicine, University of Bristol, Bristol, United Kingdom.
authors.forename: Margaret T
authors.initials: MT
authors.lastname: May
authors.affiliation: Department of Biobehavioral Health and the Center for Healthy Aging, The Pennsylvania State University, State College, Pennsylvania, United States of America.
authors.forename: Courtney A
authors.initials: CA
authors.lastname: Whetzel
authors.affiliation: Department of Biobehavioral Health, The Pennsylvania State University, State College, Pennsylvania, United States of America.
authors.forename: Elizabeth J
authors.initials: EJ
authors.lastname: Susman
authors.affiliation: Rotman Research Institute and Institute of Medical Science, University of Toronto, Toronto, Canada.
authors.forename: Tomáš
authors.initials: T
authors.lastname: Paus
mesh_terms: D000293:Adolescent; D000367:Age Factors; D002648:Child; D002940:Circadian Rhythm; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D012016:Reference Values; D012738:Sex Hormone-Binding Globulin / Q000032:analysis; D013739:Testosterone / Q000097:blood* / Q000592:standards; D055815:Young Adult
chemical_list: D012738:Sex Hormone-Binding Globulin; D013739:Testosterone