title: Are there endogenous estrone fatty acyl esters in human plasma or ovarian follicular fluid?
abstract: BACKGROUND
  Estrone and its sulfated esters are the most abundant estrogens in blood in men and in women after the menopause. However, previous studies on the esterification of estrone with fatty acids have yielded conflicting results, some studies reporting high nanomolar concentrations of estrone fatty acyl esters in plasma.
  
  
  METHODS
  We developed an estrone radioimmunoassay (RIA) method to determine endogenous concentrations of estrone and after saponification, applied it to male and female plasma. In addition, the concentration of estrone fatty acyl esters in ovarian follicular fluid was analyzed by gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-tandem mass spectrometry (LC-MS/MS).
  
  
  RESULTS
  By estrone RIA, we did not find measurable amounts of estrone fatty acyl esters in male or female plasma, except for one premenopausal woman who had the highest plasma concentration of nonesterified estrone. The concentration of hydrolyzed estrone fatty acyl esters determined by LC-MS/MS in follicular fluid obtained from women undergoing ovarian stimulation was below the limit of quantification of <10 pmol/l (<2.7 ng/l).
  
  
  CONCLUSIONS
  In contrast to previous data by others, our study suggests that estrone fatty acyl esters are in most cases not detectable in plasma of healthy men or healthy nonpregnant women.
authors.affiliation: Folkhälsan Research Center, Biomedicum Helsinki, POB 63, FIN-00014 University of Helsinki, Helsinki, Finland. veera.vihma@hus.fi
authors.forename: Veera
authors.initials: V
authors.lastname: Vihma
authors.forename: Anja
authors.initials: A
authors.lastname: Koskela
authors.forename: Ursula
authors.initials: U
authors.lastname: Turpeinen
authors.forename: Esa
authors.initials: E
authors.lastname: Hämäläinen
authors.forename: Aila
authors.initials: A
authors.lastname: Tiitinen
authors.forename: Kristiina
authors.initials: K
authors.lastname: Wähälä
authors.forename: Matti J
authors.initials: MJ
authors.lastname: Tikkanen
authors.forename: Herman
authors.initials: H
authors.lastname: Adlercreutz
mesh_terms: D000328:Adult; D000368:Aged; D002853:Chromatography, Liquid; D004952:Esters; D004970:Estrone / Q000097:blood / Q000378:metabolism*; D005260:Female; D015571:Follicular Fluid / Q000378:metabolism*; D008401:Gas Chromatography-Mass Spectrometry; D006801:Humans; D008875:Middle Aged; D011863:Radioimmunoassay; D053719:Tandem Mass Spectrometry
chemical_list: D004952:Esters; D004970:Estrone