title: Larger testes and higher inhibin B levels in Finnish than in Danish newborn boys.
abstract: BACKGROUND
  Recent studies showed that male reproductive health problems, such as cryptorchidism, hypospadias, testicular cancer, and low sperm quality, are more prevalent in Denmark than in Finland.
  
  
  OBJECTIVE
  We hypothesized that, if fetal testicular dysgenesis contributed to these observations, differences in gonadal development and the hypothalamus-pituitary-testis axis would already be detectable perinatally. Thus, we investigated healthy newborn boys in both countries.
  
  
  METHODS
  This was a prospective, longitudinal population-based study.
  
  
  METHODS
  Two primary obstetric centers were included at the University Hospitals of Copenhagen, Denmark, and Turku, Finland.
  
  
  METHODS
  The participants of the study included 633 Danish and 1044 Finnish boys, born at term with appropriate weight for gestational age.
  
  
  METHODS
  Ultrasound determination of testis size at 0, 3, and 18 months and blood sampling (n = 727) at 3 months were analyzed.
  
  
  METHODS
  Testicular volume and reproductive hormones were measured.
  
  
  RESULTS
  Testis volume was significantly higher at all ages in Finnish than in Danish boys (medians, 98 vs. 95, 185 vs. 119, and 188 vs. 136 mm(3), respectively; P < 0.00001). Testis growth from birth to 3 months was larger in Finnish than in Danish boys (mean, 75 vs. 26 mm(3); P < 0.0001). Serum hormone levels were higher in Finnish than Danish boys for inhibin B (median, 456 vs. 385 pg/ml; P < 0.0001), FSH (1.33 vs. 1.21 IU/liter; P < 0.036), and SHBG (143 vs. 136 nmol/liter; P < 0.022). Inhibin B was significantly positively correlated to testicular volume (r = 0.25; P < 0.006).
  
  
  CONCLUSIONS
  The larger testes and higher inhibin B levels most likely represent a bigger volume of seminiferous tubules in Finnish compared with Danish boys. Although this phenomenon may be attributable to a genetic difference between the two countries, it may also reflect environmental factors influencing testicular development.
authors.affiliation: University Department of Growth and Reproduction, GR 5064, Rigshospitalet, Blegdamsvej 9, DK-2100 Copenhagen, Denmark. katharina.main@rh.hosp.dk
authors.forename: Katharina M
authors.initials: KM
authors.lastname: Main
authors.forename: Jorma
authors.initials: J
authors.lastname: Toppari
authors.forename: Anne-Maarit
authors.initials: AM
authors.lastname: Suomi
authors.forename: Marko
authors.initials: M
authors.lastname: Kaleva
authors.forename: Marla
authors.initials: M
authors.lastname: Chellakooty
authors.forename: Ida M
authors.initials: IM
authors.lastname: Schmidt
authors.forename: Helena E
authors.initials: HE
authors.lastname: Virtanen
authors.forename: Kirsten A
authors.initials: KA
authors.lastname: Boisen
authors.forename: Claudia M
authors.initials: CM
authors.lastname: Kai
authors.forename: Ida N
authors.initials: IN
authors.lastname: Damgaard
authors.forename: Niels E
authors.initials: NE
authors.lastname: Skakkebaek
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001724:Birth Weight; D003718:Denmark; D005260:Female; D005387:Finland; D005640:Follicle Stimulating Hormone / Q000097:blood; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D007265:Inhibins / Q000097:blood*; D008137:Longitudinal Studies; D007986:Luteinizing Hormone / Q000097:blood; D008297:Male; D011247:Pregnancy; D011446:Prospective Studies; D012738:Sex Hormone-Binding Globulin / Q000032:analysis; D013737:Testis / Q000033:anatomy & histology* / Q000000981:diagnostic imaging / Q000254:growth & development; D014463:Ultrasonography
chemical_list: D012738:Sex Hormone-Binding Globulin; C422364:inhibin B; D007265:Inhibins; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone