title: Oral contraceptive therapy reduces serum relaxin-2 in elite female athletes.
abstract: OBJECTIVE
  Recent investigations have demonstrated that athletes with high relaxin-2 levels have a high risk of anterior cruciate ligament injuries, while athletes taking oral contraceptives (OC) have low relaxin-2 levels. It has not yet been clarified whether taking OC reduces relaxin-2 levels. The purpose of this study was to investigate changes in relaxin-2 levels in athletes taking OC.
  
  
  METHODS
  Levels of relaxin-2, estradiol, progesterone, luteinizing hormone and follicle-stimulating hormone were measured in serum samples (n = 183) from 106 elite female athletes. Five athletes with serum relaxin-2 concentrations > 6 pg/mL during the luteal phase were recruited to assess the effect of OC therapy.
  
  
  RESULTS
  Serum relaxin-2 concentrations were significantly higher during the luteal phase (n = 57) than in the follicular phase (n = 72), or in athletes on OC therapy (n = 10) (P < 0.001, P < 0.001 and P < 0.05, respectively). In the luteal phase, 36.8% (21/57) of the athletes had relaxin levels > 6 pg/mL. In 23 athletes, serum relaxin-2 concentrations were measured during both the follicular and luteal phases, revealing that relaxin-2 levels were significantly higher in the luteal phase compared with the follicular phase. In 5 out of 23 athletes, serum relaxin-2 concentrations were > 6 pg/mL in the luteal phase and during the second cycle of OC therapy, relaxin-2 concentrations decreased dramatically to below the detection limit (0.26 pg/mL).
  
  
  CONCLUSIONS
  High serum relaxin-2 concentrations were only detected during the luteal phase. In athletes with high relaxin-2 concentrations during the luteal phase, OC therapy decreased serum relaxin-2 levels.
authors.affiliation: Japan Institute of Sports Sciences, Tokyo, Japan.|Department of Obstetrics and Gynecology, University of Tokyo, Tokyo, Japan.|Department of Obstetrics and Gynecology, University of Toyama, Toyama, Japan.
authors.forename: Sayaka
authors.initials: S
authors.lastname: Nose-Ogura
authors.affiliation: Department of Obstetrics and Gynecology, University of Toyama, Toyama, Japan.
authors.forename: Osamu
authors.initials: O
authors.lastname: Yoshino
authors.affiliation: Department of Obstetrics and Gynecology, University of Toyama, Toyama, Japan.
authors.forename: Kaori
authors.initials: K
authors.lastname: Yamada-Nomoto
authors.affiliation: Japan Institute of Sports Sciences, Tokyo, Japan.
authors.forename: Mariko
authors.initials: M
authors.lastname: Nakamura
authors.affiliation: Department of Obstetrics and Gynecology, University of Tokyo, Tokyo, Japan.
authors.forename: Miyuki
authors.initials: M
authors.lastname: Harada
authors.affiliation: Japan Institute of Sports Sciences, Tokyo, Japan.
authors.forename: Michiko
authors.initials: M
authors.lastname: Dohi
authors.affiliation: Japan Institute of Sports Sciences, Tokyo, Japan.
authors.forename: Toru
authors.initials: T
authors.lastname: Okuwaki
authors.affiliation: Department of Obstetrics and Gynecology, University of Tokyo, Tokyo, Japan.
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Osuga
authors.affiliation: Japan Institute of Sports Sciences, Tokyo, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Kawahara
authors.affiliation: Department of Obstetrics and Gynecology, University of Toyama, Toyama, Japan.
authors.forename: Shigeru
authors.initials: S
authors.lastname: Saito
mesh_terms: D000328:Adult; D000568:Amenorrhea / Q000097:blood; D056352:Athletes; D003276:Contraceptives, Oral / Q000097:blood*; D004958:Estradiol / Q000097:blood; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood; D006801:Humans; D007986:Luteinizing Hormone / Q000097:blood; D008597:Menstrual Cycle / Q000097:blood; D011374:Progesterone / Q000097:blood; D012065:Relaxin / Q000097:blood*; D055815:Young Adult
chemical_list: D003276:Contraceptives, Oral; C095068:RLN2 protein, human; D011374:Progesterone; D004958:Estradiol; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone; D012065:Relaxin
keywords: anterior cruciate ligament (ACL); luteal phase; menstrual cycle; oral contraceptive (OC); relaxin-2