title: Endogenous Estrogen Regulates Somatostatin-Induced Rebound GH Secretion in Postmenopausal Women.
abstract: Systemic concentrations of T, estradiol (E2), GH, IGF-1, and IGF binding protein-3 decline in healthy aging individuals. Conversely, T and E2stimulate GH and IGF-1 production in hypogonadal patients.
  
  
  
  Because E2stimulates GH secretion, putatively via the nuclear estrogen receptor-α and E2and GH fall with menopause, we postulated that diminished endogenous E2contributes to low GH output in older women.
  
  
  
  The study was conducted at the Mayo Center for Clinical and Translational Science.
  
  
  
  This was a randomized, double-blind, controlled study in 60 healthy postmenopausal women treated with the following: 1) double placebo; 2) anastrozole, a potent inhibitor of aromatase-enzyme activity, which mediates E2synthesis from T; and/or 3) fulvestrant, a selective estrogen receptor-α antagonist.
  
  
  
  GH pulse generation was quantified by frequent GH sampling before and after short-term iv somatostatin infusion, thought to induce hypothalamic GHRH-mediated rebound-like GH secretion.
  
  
  
  On anastrozole, E2fell from 3.1 ± 0.35 pg/mL to 0.36 ± 0.04 pg/mL, and estrone from 13 ± 1.4 pg/mL to 1.9 ± 0.01 pg/mL (P < .001) by mass spectrometry. Estrogen values were unchanged by fulvestrant. T concentrations did not change. One-hour peak GH rebound after somatostatin infusion declined markedly during both estrogen-deprivation schedules (P < .001). Mean (150 min) maximal GH rebound decreased comparably (P < .001). Measures of GH rebound correlated negatively with computed tomography-estimated abdominal visceral fat (all P < .05).
  
  
  
  These data suggest a previously unrecognized dependence of hypothalamo-pituitary GH regulation on low levels of endogenous estrogen after menopause.
authors.affiliation: Endocrine Research Unit (J.D.V., D.E., R.Y.), Mayo Clinic College of Medicine, Center for Translational Science Activities, Mayo Clinic, and Department of Primary Care Internal Medicine (P.T.), Mayo Clinic, Rochester, Minnesota 55905; and Tulane University Health Sciences Center (C.B.), Endocrinology and Metabolism Section, Peptide Research Section, New Orleans, Louisiana 70112.
authors.forename: Johannes D
authors.initials: JD
authors.lastname: Veldhuis
authors.affiliation: Endocrine Research Unit (J.D.V., D.E., R.Y.), Mayo Clinic College of Medicine, Center for Translational Science Activities, Mayo Clinic, and Department of Primary Care Internal Medicine (P.T.), Mayo Clinic, Rochester, Minnesota 55905; and Tulane University Health Sciences Center (C.B.), Endocrinology and Metabolism Section, Peptide Research Section, New Orleans, Louisiana 70112.
authors.forename: Dana
authors.initials: D
authors.lastname: Erickson
authors.affiliation: Endocrine Research Unit (J.D.V., D.E., R.Y.), Mayo Clinic College of Medicine, Center for Translational Science Activities, Mayo Clinic, and Department of Primary Care Internal Medicine (P.T.), Mayo Clinic, Rochester, Minnesota 55905; and Tulane University Health Sciences Center (C.B.), Endocrinology and Metabolism Section, Peptide Research Section, New Orleans, Louisiana 70112.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Yang
authors.affiliation: Endocrine Research Unit (J.D.V., D.E., R.Y.), Mayo Clinic College of Medicine, Center for Translational Science Activities, Mayo Clinic, and Department of Primary Care Internal Medicine (P.T.), Mayo Clinic, Rochester, Minnesota 55905; and Tulane University Health Sciences Center (C.B.), Endocrinology and Metabolism Section, Peptide Research Section, New Orleans, Louisiana 70112.
authors.forename: Paul
authors.initials: P
authors.lastname: Takahashi
authors.affiliation: Endocrine Research Unit (J.D.V., D.E., R.Y.), Mayo Clinic College of Medicine, Center for Translational Science Activities, Mayo Clinic, and Department of Primary Care Internal Medicine (P.T.), Mayo Clinic, Rochester, Minnesota 55905; and Tulane University Health Sciences Center (C.B.), Endocrinology and Metabolism Section, Peptide Research Section, New Orleans, Louisiana 70112.
authors.forename: Cyril
authors.initials: C
authors.lastname: Bowers
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000077384:Anastrozole; D047072:Aromatase Inhibitors / Q000008:administration & dosage / Q000494:pharmacology*; D004311:Double-Blind Method; D004958:Estradiol / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000378:metabolism* / Q000494:pharmacology; D065171:Estrogen Receptor Antagonists / Q000008:administration & dosage / Q000494:pharmacology*; D047628:Estrogen Receptor alpha / Q000037:antagonists & inhibitors*; D005260:Female; D000077267:Fulvestrant; D019382:Human Growth Hormone / Q000378:metabolism*; D006801:Humans; D008875:Middle Aged; D009570:Nitriles / Q000008:administration & dosage / Q000494:pharmacology*; D017698:Postmenopause / Q000097:blood*; D013004:Somatostatin / Q000008:administration & dosage / Q000494:pharmacology*; D014230:Triazoles / Q000008:administration & dosage / Q000494:pharmacology*
chemical_list: D047072:Aromatase Inhibitors; C506487:ESR1 protein, human; D065171:Estrogen Receptor Antagonists; D047628:Estrogen Receptor alpha; D009570:Nitriles; D014230:Triazoles; D019382:Human Growth Hormone; D000077267:Fulvestrant; D000077384:Anastrozole; D004958:Estradiol; D013004:Somatostatin