title: Impact of fatness, fitness, and ethnicity on the relationship of nocturnal ghrelin to 24-hour luteinizing hormone concentrations in adolescent girls.
abstract: BACKGROUND
  Ghrelin is related to energy balance that regulates food intake.
  
  
  OBJECTIVE
  The aim was to explore whether ghrelin would be linked to differences in fitness in adolescent girls, whose menstrual cycles are sensitive to changes in energy balance.
  
  
  METHODS
  A total of 72 girls, ages 14-21 yr, including five with amenorrhea, were studied in the follicular phase. LH was sampled every 10 min over 24-h, and ghrelin was measured hourly between 2300 and 0300 h. Body composition was measured by dual x-ray absorptiometry. Fitness was characterized by reported frequency of exercise per week and by maximal oxygen consumption with "high" vs. "low" fitness groups defined from maximal oxygen consumption norms for this population. Data were analyzed with SAS software (SAS Institute Inc., Cary, NC).
  
  
  RESULTS
  Ghrelin was related to percent body fat (P = 0.038; R(2) 0.07), weekly exercise (P = 0.032; R(2) 0.07), and 24-h mean LH (P = 0.002; R(2) 0.13). The ghrelin relationship with LH was more pronounced in the low-fitness group. In multiple regression models, 24-h LH was an independent predictor of ghrelin after adjusting for percent body fat, fitness, exercise, or age. Ghrelin was higher in Caucasian girls than in African-American girls after adjusting for covariates at 0200 h (P = 0.017).
  
  
  CONCLUSIONS
  Twenty-four-hour LH is an independent predictor of nighttime ghrelin concentrations in postpubertal adolescent girls. Diverging patterns in ghrelin may reflect differences in exercise patterns and/or may be influenced by ethnicity. These data introduce ghrelin as a biomarker of individual differences in energy balance during the menstrual cycle and across ethnicities.
authors.affiliation: Department of Pediatrics, University of Michigan Medical Center, Ann Arbor, Michigan 48019-0718, USA. jzkv@umich.edu
authors.forename: J Z
authors.initials: JZ
authors.lastname: Kasa-Vubu
authors.forename: A
authors.initials: A
authors.lastname: Rosenthal
authors.forename: E G
authors.initials: EG
authors.lastname: Murdock
authors.forename: K B
authors.initials: KB
authors.lastname: Welch
mesh_terms: D015502:Absorptiometry, Photon; D050154:Adiposity / Q000502:physiology*; D000293:Adolescent; D001741:Black or African American; D015308:Anaerobic Threshold / Q000502:physiology; D000704:Analysis of Variance; D001213:Asian; D004734:Energy Metabolism / Q000502:physiology; D005006:Ethnicity; D015444:Exercise / Q000502:physiology; D005260:Female; D054439:Ghrelin; D006801:Humans; D007986:Luteinizing Hormone / Q000097:blood*; D008597:Menstrual Cycle / Q000502:physiology; D036361:Peptide Hormones / Q000097:blood*; D010809:Physical Fitness / Q000502:physiology*; D010865:Pilot Projects; D011627:Puberty / Q000378:metabolism / Q000502:physiology; D012044:Regression Analysis; D044465:White People
chemical_list: D054439:Ghrelin; D036361:Peptide Hormones; D007986:Luteinizing Hormone