title: The distribution of FSH receptor isoforms is related to basal FSH levels in subfertile women with normal menstrual cycles.
abstract: BACKGROUND
  Recently a polymorphic variant of the FSH receptor in which amino acid asparagine (Asn) at position 680 is replaced by serine (Ser) was found. This is associated with higher FSH levels in the early follicular phase and an increased FSH requirement to obtain follicular response in IVF patients. The aim of our study was to test the hypothesis that this receptor isoform occurs more often in regularly menstruating subfertility patients with elevated basal FSH than in those with normal early follicular phase FSH.
  
  
  METHODS
  A retrospective cohort study of 38 subfertility patients with a regular menstrual cycle and elevated FSH (>10 IU/l) compared to 40 patients with normal early follicular phase FSH was carried out. DNA was analysed to determine the FSH receptor genotype.
  
  
  RESULTS
  The N680S variant on one or both alleles of the FSH receptor gene was significantly more prevalent in patients with elevated FSH (P < 0.05). The homozygous Asn/Asn variant at codon 680 was found in 45% of women with normal FSH and in 21% of women with elevated FSH. The homozygous Ser/Ser receptor variant was present in 12.5% of women with normal FSH and in 21% of patients with elevated FSH. Also the heterozygous combination of both variants Asn/Ser occurred more often in women with elevated FSH (58 versus 42.5%).
  
  
  CONCLUSIONS
  The N680S sequence variation of the FSH receptor is found in >75% of the cases with elevated basal FSH and suggests a higher FSH threshold.
authors.affiliation: Division of Reproductive Medicine, Department of Obstetrics and Gynaecology, Vrije Universiteit Medical Centre, P.O.Box 7057, 1007 MB Amsterdam, The Netherlands.
authors.forename: C H
authors.initials: CH
authors.lastname: de Koning
authors.forename: T
authors.initials: T
authors.lastname: Benjamins
authors.forename: P
authors.initials: P
authors.lastname: Harms
authors.forename: R
authors.initials: R
authors.lastname: Homburg
authors.forename: J M
authors.initials: JM
authors.lastname: van Montfrans
authors.forename: J
authors.initials: J
authors.lastname: Gromoll
authors.forename: M
authors.initials: M
authors.lastname: Simoni
authors.forename: C B
authors.initials: CB
authors.lastname: Lambalk
mesh_terms: D000328:Adult; D005260:Female; D005298:Fertility; D005640:Follicle Stimulating Hormone / Q000097:blood*; D014644:Genetic Variation; D005838:Genotype; D006801:Humans; D008597:Menstrual Cycle / Q000097:blood / Q000235:genetics; D011110:Polymorphism, Genetic; D020033:Protein Isoforms / Q000235:genetics; D011962:Receptors, FSH / Q000235:genetics*; D012189:Retrospective Studies
chemical_list: D020033:Protein Isoforms; D011962:Receptors, FSH; D005640:Follicle Stimulating Hormone