title: Peripheral plasma met-enkephalin levels in ovulatory and anovulatory human menstrual cycles.
abstract: OBJECTIVE
  To test the hypothesis that met-enkephalin has a role in human ovulation and that plasma levels may differ between ovulatory and anovulatory ovarian cycles.
  
  
  METHODS
  This is a descriptive study comparing levels of plasma met-enkephalin, gonadotropins, and ovarian steroids in 12 ultrasonically confirmed ovulatory cycles and 12 anovulatory cycles.
  
  
  METHODS
  The study took place in the infertility clinic of a large teaching hospital receiving primary and tertiary referrals of both private and public sector patients.
  
  
  METHODS
  All patients (n = 16) had infertility greater than or equal to 3 years and normal findings on previous investigation including evidence of ovulation.
  
  
  METHODS
  Ovarian cycles were defined using transabdominal ultrasound scanning. Biochemical analyses were by radioimmunoassay.
  
  
  METHODS
  The differences between plasma met-enkephalin levels in the two groups of cycles were compared.
  
  
  RESULTS
  Met-enkephalin levels are significantly higher in ovulatory cycles with a significant peak in the 2 postovulatory days (Duncan's multiple range test; P less than 0.05).
  
  
  CONCLUSIONS
  Human ovulation is associated with cyclic elevation of plasma met-enkephalin. Further studies are required to elucidate causality.
authors.affiliation: Department of Obstetrics and Gynaecology, St. James's University Hospital, Leeds, United Kingdom.
authors.forename: E A
authors.initials: EA
authors.lastname: Saad
authors.forename: D R
authors.initials: DR
authors.lastname: Bromham
authors.forename: K
authors.initials: K
authors.lastname: Bhabra
authors.forename: C L
authors.initials: CL
authors.lastname: Ambrose
mesh_terms: D000858:Anovulation / Q000097:blood*; D004744:Enkephalin, Methionine / Q000097:blood*; D004958:Estradiol / Q000097:blood; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood; D006801:Humans; D007247:Infertility, Female / Q000097:blood*; D007986:Luteinizing Hormone / Q000097:blood; D008597:Menstrual Cycle / Q000502:physiology*; D010060:Ovulation / Q000502:physiology*; D011374:Progesterone / Q000097:blood
chemical_list: D011374:Progesterone; D004958:Estradiol; D004744:Enkephalin, Methionine; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone