title: Familial coaggregation of cryptorchidism, hypospadias, and testicular germ cell cancer: a nationwide cohort study.
abstract: BACKGROUND
  Cryptorchidism, hypospadias, and testicular germ cell cancer (TGCC) may be symptoms of a testicular dysgenesis syndrome that manifests during fetal life. To address the inheritability of this syndrome, we examined whether family history of cryptorchidism or hypospadias is associated with an increased risk of TGCC.
  
  
  METHODS
  A total of 2,159,883 men born since 1953, identified through Danish health registers, were followed from April 2, 1968, through May 31, 2008. First-, second-, and third-degree relatives were identified in the Danish Family Relations Database; cryptorchidism and hypospadias patients were identified in the Danish Hospital Discharge Register; and TGCC patients were identified in the Danish Cancer Register. Poisson regression was used to calculate the risk ratio for TGCC by family history of cryptorchidism or hypospadias.
  
  
  RESULTS
  A total of 5441 patients developed TGCC. A personal history of cryptorchidism or hypospadias was associated with an increased relative risk (RR) of developing TGCC (RR = 3.71, 95% confidence interval [CI] = 3.29 to 4.19; and RR = 2.13, 95% CI = 1.26 to 3.61, respectively). For example, in men in their thirties, the overall rate per 100 000 is 25.1 in the cohort, but 88.6 and 55.4 in men born with cryptorchidism or hypospadias, respectively. In contrast, relatives of a hypospadias patient did not have a statistically significantly increased risk of TGCC nor did the first- and second-degree relatives of cryptorchidism patients. However, we found a small increased risk of TGCC for third-degree relatives of patients with cryptorchidism.
  
  
  CONCLUSIONS
  Having hypospadias or cryptorchidism was associated with an increased risk of developing TGCC. However, our finding that family history of hypospadias or cryptorchidism generally was not associated with increased risk of developing TGCC does not support the hypothesis of shared inheritability of cryptorchidism, hypospadias, and TGCC.
authors.affiliation: Department of Epidemiology Research, Statens Serum Institut, Artillerivej 5, 2300 Copenhagen S, Denmark. tsh@ssi.dk
authors.forename: Tine H
authors.initials: TH
authors.lastname: Schnack
authors.forename: Gry
authors.initials: G
authors.lastname: Poulsen
authors.forename: Charlotte
authors.initials: C
authors.lastname: Myrup
authors.forename: Jan
authors.initials: J
authors.lastname: Wohlfahrt
authors.forename: Mads
authors.initials: M
authors.lastname: Melbye
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D003456:Cryptorchidism / Q000453:epidemiology* / Q000235:genetics*; D003718:Denmark / Q000453:epidemiology; D018237:Germinoma / Q000453:epidemiology* / Q000235:genetics*; D006801:Humans; D007021:Hypospadias / Q000453:epidemiology* / Q000235:genetics*; D015994:Incidence; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008875:Middle Aged; D016012:Poisson Distribution; D012042:Registries; D018570:Risk Assessment; D012307:Risk Factors; D013736:Testicular Neoplasms / Q000453:epidemiology* / Q000235:genetics*; D055815:Young Adult