Cryptorchidism concordance in monozygotic and dizygotic twin brothers, full brothers, and half-brothers.
OBJECTIVE
To study concordance rates of cryptorchidism (undescended testis) in pairs of boys with varying family structure, to evaluate the risk contribution from the intrauterine environment and genetic factors.


METHODS
Population based study of 1,024,500 Danish boys born from January 1, 1973 to December 31, 2004. Classic twin method and computerized square dance design.


METHODS
Hospitals and outpatient clinics.


METHODS
Six groups of boy pairs: boys with no relation, paternal half-brothers, maternal half-brothers, full brothers, dizygotic twin brothers, and monozygotic twin brothers.


METHODS
Observational study.


METHODS
Status on each individual regarding cryptorchidism and orchiopexy from the Danish National Patient Register.


RESULTS
Concordance rates of cryptorchidism in the groups were as follows: boys with no relation 3.2% (95% confidence interval 2.7%-3.6%), paternal half-brothers 3.4% (2.3%-4.7%), maternal half-brothers 6.0% (4.5%-7.7%), full brothers 8.8% (8.3%-9.8%), dizygotic twin brothers 24.1% (16.0%-33.6%), and monozygotic twin brothers 27.3% (15.5%-41.2%).


CONCLUSIONS
The concordance rate was higher in maternal than in paternal half-brothers, and much higher but of equal magnitude in both twin groups. The findings strongly support that the intrauterine environment and maternal inheritance are contributing to the occurrence of cryptorchidism.
Jensen
Morten Søndergaard
MS
Department of Occupational Medicine, Aarhus University Hospital, Aarhus, Denmark. morten@sondergaard-jensen.dk
Toft
Gunnar
G
Thulstrup
Ane Marie
AM
Henriksen
Tine Brink
TB
Olsen
Jørn
J
Christensen
Kaare
K
Bonde
Jens Peter
JP
D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D003456:Cryptorchidism / Q000235:genetics* / Q000601:surgery; D003718:Denmark; D004777:Environment; D020022:Genetic Predisposition to Disease; D040941:Heredity; D006801:Humans; D016015:Logistic Models; D008297:Male; D016017:Odds Ratio; D056126:Orchiopexy; D010375:Pedigree; D012042:Registries; D018570:Risk Assessment; D012307:Risk Factors; D014429:Twins, Dizygotic / Q000235:genetics*; D014430:Twins, Monozygotic / Q000235:genetics*; D055815:Young Adult