title: Gonadotropin responses to estrogen-positive and -negative feedback are identical in African-American and Caucasian women.
abstract: BACKGROUND
  Gonadotropin levels are similar in African-American women (AAW) and Caucasian women (CW), despite higher preovulatory estradiol (E2) levels in AAW, suggesting that AAW may be less sensitive to E2 feedback than CW.
  
  
  OBJECTIVE
  The aim of the study was to determine whether responsivity to estrogen feedback differs in AAW and CW.
  
  
  METHODS
  Subjects were studied in the early follicular phase using a 5-d, graded E2 and progesterone infusion.
  
  
  METHODS
  Healthy, normal-cycling AAW (n = 10) and CW (n = 13) aged 23-30 yr participated in the study.
  
  
  METHODS
  Blood samples were collected every 4 h and assayed for LH, FSH, E2, and progesterone.
  
  
  RESULTS
  There was no difference in E2-negative feedback on LH (nadir, 3.8 ± 0.4 vs. 5.4 ± 0.9 IU/liter; time of nadir, 33.2 ± 3.3 vs. 32.3 ± 2.7 h) or FSH (nadir, 3.1 ± 0.4 vs. 3.1 ± 0.3 IU/liter; time of nadir, 48.8 ± 2.7 vs. 50.5 ± 3.1 h) in AAW compared to CW. The two groups also demonstrated similar positive feedback responses of E2 on LH (peak, 80.3 ± 13.3 vs. 73.1 ± 11.6 IU/liter; time of peak, 80.4 ± 4.3 vs. 86.5 ± 3.1 h) and FSH (peak, 13.4 ± 1.4 vs. 10.2 ± 1.0 IU/liter; time of peak, 82.2 ± 4.0 vs. 97.2 ± 4.9 h).
  
  
  CONCLUSIONS
  LH and FSH feedback responses to a controlled steroid infusion do not differ between AAW and CW, indicating that AAW do not have diminished hypothalamic-pituitary responsivity to E2. These studies support the concept of a threshold effect of E2 in generating LH-positive feedback, suggest pituitary insensitivity to differences in E2 of the magnitude observed in prior studies, and account for similarities in gonadotropins despite E2 differences in AAW compared with CW.
authors: Reproductive Endocrine Unit, Department of Medicine, Massachusetts General Hospital, 55 Fruit Street, Boston, Massachusetts 02114, USA.
authors: N D
authors: ND
authors: Shaw
authors: K M
authors: KM
authors: Klingman
authors: S S
authors: SS
authors: Srouji
authors: S N
authors: SN
authors: Histed
authors: J E
authors: JE
authors: Hall
mesh_terms: D000328:Adult; D001741:Black or African American; D015992:Body Mass Index; D004958:Estradiol / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D025461:Feedback, Physiological / Q000187:drug effects*; D005260:Female; D006062:Gonadotropins / Q000097:blood* / Q000378:metabolism; D006801:Humans; D007260:Infusion Pumps; D008597:Menstrual Cycle / Q000097:blood / Q000187:drug effects / Q000378:metabolism; D011374:Progesterone / Q000008:administration & dosage / Q000097:blood / Q000378:metabolism; D044465:White People; D055815:Young Adult
chemical_list: D006062:Gonadotropins; D011374:Progesterone; D004958:Estradiol