title: Attenuation of the oestrogen positive feedback mechanism with the age in postmenopausal women.
abstract: OBJECTIVE
  It has been reported that the positive feedback mechanism of oestrogens and progesterone is preserved, although attenuated, in late postmenopausal years. Whether this is also true for the positive feedback effect of oestrogens alone has not been investigated.
  
  
  METHODS
  Prospective intervention study.
  
  
  METHODS
  Thirty healthy postmenopausal women.
  
  
  METHODS
  The women were divided into three groups according to the years since menopause (group I: 2-8 years, group II: 9-17 years, group III: 18-25 years). They were studied during a period of 41 days. Two acute experiments (EP) of exogenous oestradiol, given via skin patches, were performed from days 1 to 7 (EP1) and from days 35 to 41 (EP2) to induce an LH surge. Between the two experiments (days 7-34), oestradiol was given at the dose of 100 μg every 3 days, while oral progesterone was added from day 21 to day 34 in order to simulate a luteal phase. Blood samples were taken every 6 h during EP1 and EP2 as well as on days 8, 13, 20, 21, 27 and 34. FSH, LH, oestradiol and progesterone were measured in all blood samples.
  
  
  RESULTS
  An LH surge occurred as a result of the oestradiol positive feedback mechanism in group I and in group II, in both EP1 and EP2. Peak LH values during the surge were significantly lower in group II than in group I in both experiments. None of the patients in group III displayed an LH surge.
  
  
  CONCLUSIONS
  These results demonstrate for the first time a gradual attenuation of the pituitary response to oestrogenic provocation over a certain period following the menopause, with complete abolition after 20 years. It is suggested that the reserves of pituitary gonadotrophs diminish with age.
authors: Department of Obstetrics and Gynaecology, School of Health Sciences, Faculty of Medicine, University of Thessaly, Larissa, Greece.
authors: Marina
authors: M
authors: Dimitraki
authors: Department of Obstetrics and Gynaecology, Medical School, University of Thrace, Alexandroupolis, Greece.
authors: Nikoletta
authors: N
authors: Koutlaki
authors: Department of Obstetrics and Gynaecology, Medical School, University of Thrace, Alexandroupolis, Greece.
authors: Theodora
authors: T
authors: Gioka
authors: Department of Obstetrics and Gynaecology, School of Health Sciences, Faculty of Medicine, University of Thessaly, Larissa, Greece.
authors: Christina I
authors: CI
authors: Messini
authors: Department of Obstetrics and Gynaecology, School of Health Sciences, Faculty of Medicine, University of Thessaly, Larissa, Greece.
authors: Konstantinos
authors: K
authors: Dafopoulos
authors: Department of Obstetrics and Gynaecology, School of Health Sciences, Faculty of Medicine, University of Thessaly, Larissa, Greece.
authors: George
authors: G
authors: Anifandis
authors: Department of Obstetrics and Gynaecology, School of Health Sciences, Faculty of Medicine, University of Thessaly, Larissa, Greece.
authors: Ioannis E
authors: IE
authors: Messinis
mesh_terms: D000368:Aged; D004334:Drug Administration Schedule; D004958:Estradiol / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology; D004967:Estrogens / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D025461:Feedback, Physiological / Q000187:drug effects* / Q000502:physiology; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood; D006801:Humans; D008183:Luteal Phase / Q000097:blood / Q000187:drug effects* / Q000502:physiology; D007986:Luteinizing Hormone / Q000097:blood; D008875:Middle Aged; D017698:Postmenopause / Q000097:blood / Q000187:drug effects* / Q000502:physiology; D011374:Progesterone / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology; D011372:Progestins / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology; D011446:Prospective Studies; D013997:Time Factors
chemical_list: D004967:Estrogens; D011372:Progestins; D011374:Progesterone; D004958:Estradiol; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone