title: Familial coaggregation of cryptorchidism and hypospadias.
abstract: BACKGROUND
  It has been suggested that cryptorchidism and hypospadias may be the result of a common pathologic pathway that causes testicular dysgenesis during fetal life. To address the potential heritability of this pathway, we specifically examined to what extent a family history of cryptorchidism increases the risk of developing hypospadias and vice versa.
  
  
  METHODS
  By using Danish health registers, we identified 27,762 boys diagnosed with cryptorchidism and 4832 boys diagnosed with hypospadias in a cohort of 1,018,517 boys born during 1977-2005. Using binomial log-linear regression, we estimated risk ratios of cryptorchidism and hypospadias in male twin pairs and first-, second-, and third-degree relatives with a family history of hypospadias and cryptorchidism, respectively.
  
  
  RESULTS
  After adjusting for birth period and personal hypospadias/cryptorchidism status, there was little evidence of increased risk of cryptorchidism given a family history of hypospadias, and vice versa. However, cryptorchidism and hypospadias was associated on an individual level.
  
  
  CONCLUSIONS
  We found no persuasive evidence that a family history of hypospadias increases the risk of cryptorchidism and vice versa. Thus, we found no support for shared heritability of hypospadias and cryptorchidism.
authors.affiliation: Department of Epidemiology Research, Statens Serum Institute, 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: D003456:Cryptorchidism / Q000453:epidemiology / Q000235:genetics*; D003718:Denmark / Q000453:epidemiology; D005190:Family; D020022:Genetic Predisposition to Disease; D006801:Humans; D007021:Hypospadias / Q000453:epidemiology / Q000235:genetics*; D040582:Inheritance Patterns; D016014:Linear Models; D008297:Male; D016017:Odds Ratio; D012042:Registries; D018570:Risk Assessment; D014427:Twins / Q000235:genetics