title: Androgen receptor gene GGN repeat length and reproductive characteristics in young Swedish men.
abstract: BACKGROUND
  The human androgen receptor (AR) gene contains two polymorphisms of CAG and GGN repeats respectively. The GGN repeat function is still largely unknown and to date there are no in vivo data on this segment with respect to the general population.
  
  
  METHODS
  We investigated the impact of CAG and GGN repeats on male reproductive function, one by one and in interaction with each other, in 220 adolescent men from the general Swedish population. Physical examination and semen analysis, including accessory sex gland markers and measurement of reproductive hormone levels, were performed. Lifestyle-associated factors, including maternal smoking during pregnancy, were recorded. GGN and CAG repeat lengths were determined by sequencing.
  
  
  RESULTS
  GGN<23 was associated with lower semen volume when compared to GGN=23 (mean difference -0.6 ml, P=0.02) and GGN>23 (mean difference -0.9 ml, P=0.002). Men with GGN<23, exposed to maternal smoking during pregnancy, had higher body mass index compared to men with other GGN lengths, no matter whether their mother had smoked or not during pregnancy (mean difference 4.8 kg/m2, P<0.001).
  
  
  CONCLUSIONS
  Short GGN repeats seem to be associated with decreased semen volume, possibly due to suboptimal AR activity. Body composition may be influenced by the combination of fetal exposure to maternal smoking and certain AR genotypes.
authors.affiliation: Molecular Reproductive Medicine Research Unit, Department of Clinical Sciences, Lund University, Fertility Centre, Malmö University Hospital, SE-205 02 Malmö, Sweden.
authors.forename: K B
authors.initials: KB
authors.lastname: Lundin
authors.forename: Y L
authors.initials: YL
authors.lastname: Giwercman
authors.forename: L
authors.initials: L
authors.lastname: Rylander
authors.forename: L
authors.initials: L
authors.lastname: Hagmar
authors.forename: A
authors.initials: A
authors.lastname: Giwercman
mesh_terms: D000293:Adolescent; D000328:Adult; D015415:Biomarkers; D015992:Body Mass Index; D005260:Female; D005838:Genotype; D006801:Humans; D008297:Male; D011110:Polymorphism, Genetic; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects; D011944:Receptors, Androgen / Q000235:genetics*; D012098:Reproduction / Q000235:genetics*; D012661:Semen; D012907:Smoking; D013548:Sweden; D018911:Trinucleotide Repeats / Q000235:genetics*
chemical_list: D015415:Biomarkers; D011944:Receptors, Androgen