Age-dependent effect on contralateral testicular compensation after testicular loss

Objective

To study compensatory changes in testicular growth and the hormonal axis after unilateral orchiectomy in a neonatal, prepubertal, and pubertal/adult murine model. This is the first study to use a neonatal mouse survival surgery model.

Design

A laboratory-based study examining a control, neonatal, prepubertal, and pubertal/adult mouse model.

Setting

University-based basic science research laboratory.

Animals

Control, neonatal (2–4 days of life), prepubertal (12–21 days of life), and pubertal/adult (42–44 days of life) C57BL/6 mouse models.

Intervention

Unilateral orchiectomy in the neonatal, prepubertal, and pubertal/adult mouse models at their respective ages.

Main Outcome Measures

Body and testis weight and testicular length in the long axis were measured in a blinded fashion. In a similar way, testosterone, luteinizing hormone (LH), and follicle-stimulating hormone were assessed.

Results

Testes from neonatal and prepubertal mice weighed more (110.5, 12.2 and 103.0, 7.2 mg, respectively) than the control mice (91, 11.9 mg). There was no difference between the postpubertal group and the control group. The degree of compensatory hypertrophy was greater in the neonatal group but not in the prepubertal group when compared with the postpubertal group. Differences in follicle-stimulating hormone and testosterone were not statistically significant between the experimental and control arms. LH was significantly elevated in all experimental groups compared with the control.

Conclusions

This is the first study to assess testicular compensatory hypertrophy using a neonatal mouse survival surgery model. Testicular hypertrophy occurs when unilateral loss occurs before puberty, but not in adulthood in mice. Earlier testis loss may contribute to a greater degree of growth. Functionally, the unilateral testis can maintain eugonadal testosterone levels, but higher levels of LH are required after hemicastration to sustain eugonadal testosterone levels.