title: Oxytocin secretion is related to measures of energy homeostasis in young amenorrheic athletes.
abstract: BACKGROUND
  Oxytocin has been implicated in the modulation of energy metabolism in animals. Oxytocin knockout mice develop obesity without a change in food intake, suggesting that a lack of oxytocin may reduce metabolic rate. Furthermore, administration of oxytocin centrally reduces food intake in rats, an effect reversed by an oxytocin antagonist, implying that oxytocin may regulate appetite and energy intake. We have previously demonstrated that young female athletes (in a higher energy expenditure state than nonathletes) have low nocturnal oxytocin compared with nonathletes. Whether oxytocin is associated with measures of energy homeostasis in athletes is unknown.
  
  
  OBJECTIVE
  We hypothesized that oxytocin, a signal for energy availability, would be associated with other measures of energy homeostasis in young female athletes.
  
  
  METHODS
  We performed a cross-sectional study of 45 females, aged 14-21 years [15 amenorrheic athletes (AA), 15 eumenorrheic athletes, and 15 nonathletes] of comparable body mass index.
  
  
  METHODS
  Dual x-ray absorptiometry was performed to assess body composition. Indirect calorimetry was used to measure resting energy expenditure (REE). Fasting levels of oxytocin, energy homeostasis hormones irisin and fibroblast growth factor-21, and appetite-regulating hormone peptide YY were obtained.
  
  
  RESULTS
  In AA, oxytocin secretion was positively correlated with surrogate measures of energy availability, including weight (r = 0.65, P = .009) and body mass index (r = 0.61, P = .016). Furthermore, oxytocin was associated with REE (r = 0.80, P = .0003), independent of lean mass, and with irisin (r = 0.74, P = .002) and fibroblast growth factor-21 (r = 0.58, P = .024). In eumenorrheic athletes, oxytocin was associated with REE (r = 0.59, P = .021), independent of lean mass. In nonathletes, oxytocin secretion was not significantly associated with measures of energy homeostasis.
  
  
  CONCLUSIONS
  In AA, oxytocin secretion is associated with measures of energy availability and expenditure, suggesting that oxytocin may be involved in regulation of energy balance in energy deficient states. Further studies determining the role of oxytocin in appetite and energy homeostasis in athletes are warranted.
authors.affiliation: Neuroendocrine Unit (E.A.L., K.E.A., M.S., D.A.M., H.C., M.M.), Department of Medicine, Massachusetts General Hospital and Harvard Medical School, and Pediatric Endocrine Unit (M.M.), Massachusetts General Hospital for Children and Harvard Medical School, Boston Massachusetts 02114; and Division of Sports Medicine (K.E.A.), Department of Orthopedics, Boston Children's Hospital and Harvard Medical School, Boston Massachusetts 02115.
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Lawson
authors.forename: Kathryn E
authors.initials: KE
authors.lastname: Ackerman
authors.forename: Meghan
authors.initials: M
authors.lastname: Slattery
authors.forename: Dean A
authors.initials: DA
authors.lastname: Marengi
authors.forename: Hannah
authors.initials: H
authors.lastname: Clarke
authors.forename: Madhusmita
authors.initials: M
authors.lastname: Misra
mesh_terms: D000293:Adolescent; D000568:Amenorrhea / Q000097:blood / Q000378:metabolism*; D056352:Athletes; D015992:Body Mass Index; D001835:Body Weight / Q000502:physiology; D002153:Calorimetry, Indirect; D003430:Cross-Sectional Studies; D004734:Energy Metabolism / Q000502:physiology*; D005260:Female; D005346:Fibroblast Growth Factors / Q000097:blood; D005353:Fibronectins / Q000097:blood; D006801:Humans; D010121:Oxytocin / Q000097:blood*; D055815:Young Adult
chemical_list: C577593:FNDC5 protein, human; D005353:Fibronectins; C414620:fibroblast growth factor 21; D010121:Oxytocin; D005346:Fibroblast Growth Factors