title: Form and function of the corpus luteum during the human menstrual cycle.
abstract: OBJECTIVE
  To characterize the growth and regression of the corpus luteum (CL) during an interovulatory interval (IOI) using serial transvaginal ultrasonography.
  
  
  METHODS
  Fifty healthy women of reproductive age with a history of regular menstrual cycles underwent daily transvaginal ultrasonography for one IOI. Measurements of luteal area and luteal numerical pixel value (NPV) were recorded each day after ovulation until the CL could no longer be detected. Blood was drawn every third day during the IOI to measure serum concentrations of progesterone and estradiol-17beta.
  
  
  RESULTS
  Corpora lutea were of two morphological types: those with a central fluid-filled cavity (CFFC) (78%) and those without (22%). Eighty-eight percent of women exhibited a CL containing a CFFC 2 days after ovulation, followed by 34% 13 days after ovulation and 2% 27 days after ovulation. Luteal area, progesterone concentration and estradiol concentration increased for approximately the first 6 days following ovulation followed by a subsequent decline. Luteal NPV decreased from days 1 to 11 and increased during days 11-16. Changes in luteal area, NPV, progesterone and estradiol concentrations did not differ in women with two versus three waves of follicular development.
  
  
  CONCLUSIONS
  Peak luteal function, as determined by maximum luteal area, progesterone concentration and estradiol concentration, is observed 6 days following ovulation. Luteal NPV is reflective of morphological and endocrinological changes in the CL. The development of a CFFC during luteinization is a normal physiological phenomenon. The CL can be detected, but is not functional, during the follicular phase of the menstrual cycle.
authors.affiliation: Women's Health Imaging Research Laboratory, Department of Obstetrics, Gynecology and Reproductive Sciences, Royal University Hospital, University of Saskatchewan, Saskatoon, Saskatchewan, Canada.
authors.forename: A R
authors.initials: AR
authors.lastname: Baerwald
authors.forename: G P
authors.initials: GP
authors.lastname: Adams
authors.forename: R A
authors.initials: RA
authors.lastname: Pierson
mesh_terms: D000328:Adult; D003338:Corpus Luteum / Q000000981:diagnostic imaging* / Q000502:physiology*; D004958:Estradiol / Q000097:blood; D005260:Female; D005498:Follicular Phase / Q000502:physiology; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008183:Luteal Phase / Q000502:physiology; D008597:Menstrual Cycle / Q000502:physiology*; D006080:Ovarian Follicle / Q000000981:diagnostic imaging; D010060:Ovulation / Q000502:physiology; D011374:Progesterone / Q000097:blood; D014463:Ultrasonography
chemical_list: D011374:Progesterone; D004958:Estradiol