CONTEXT: The pattern of testicular growth during puberty may provide important information about early testicular damage and reproductive potential in adulthood.

OBJECTIVE: To evaluate pubertal testicular growth in boys with congenital cryptorchidism and controls.

DESIGN: Longitudinal case-control study.

SETTING: Andrological Research Center, University of Turku.

PARTICIPANTS: Altogether, 119 boys participated: 51 cases with a history of congenital cryptorchidism and 65 controls fulfilled the inclusion criteria.

INTERVENTION: None.

MAIN OUTCOME MEASURES: Testicular volume by an orchidometer (mL) and ultrasound (mL), testicular length by a ruler (mm), and onset of pubertal testicular growth (y). Longitudinal testicular growth was analyzed with a nonlinear mixed-effect model.

RESULTS: The mean age of the onset of pubertal testicular growth (age at the attainment of >3 mL by orchidometer) was 11.7 and 11.8 years in cryptorchid cases and controls, respectively. The difference between cases and controls was not significant. Modeled postpubertal testicular size was smaller among bilaterally and unilaterally undescended testis than in controls. There was a high level of agreement between testicular sizes of 3 mL by orchidometer and 25 mm by ruler as cut-offs in definition of the onset of puberty. An orchidometer size of 3 mL and ruler length of 25 mm corresponded to 1.6 and 1.7 mL by ultrasound (with Lambert's formula), respectively.

CONCLUSIONS: Testicular growth in puberty was impaired in congenitally cryptorchid boys. This suggests a poor perinatal development of the cryptorchid testis. The timing of the onset of pubertal testicular growth, however, did not differ which suggests an intact hypothalamic-pituitary axis.