Endocrine Abstracts

Background: Testicular ultrasound (US) is routinely employed in the evaluation of reproductive and sexual function. However, its use for characteristics other than testicular volume is hampered by a lack of information on the prognostic value of its findings, that to date have only been incorporated in a score proposed by Lenz et al. in 1993.

Objectives: We sought to explore whether testicular US examination can predict spermatogenesis and provide information on testicular endocrine function.

Materials and methods: We retrospectively reviewed 6210 testicular US examinations, finally selecting examinations from 2230 unique men after exclusion of individuals younger than 17 years of age and those affected by congenital disorders known to affect the testes. The following variables were considered: bitesticular volume (BTV), echotexture, echogenicity and presence of microlithiasis, solid lesions and varicocele; testicular asymmetry was derived via the testicular atrophy index. Concurrent fasting hormonal data were available for 1160 men, while 979 had a semen sample available from the same day as the US exam. We defined hypogonadism as total testosterone <12 nmol/l and LH > 8.16 mIU/ml and employed a sperm synthetic index to identify impaired spermatogenesis, defined as the total number of motile spermatozoa with a normal morphology (using a cut-off of 0.625 × 10⁶/ejaculate, derived from the 5th centiles of the WHO 2010 reference parameters (39 × 10⁶ spermatozoa × 40% motility × 4% normal forms).

Results: Through linear and logistic regression analyses BTV and testicular echostructure were independent predictors of sperm concentration, total sperm number, total motility, normal forms and sperm synthetic index (P < 0.001 for all), while the addition of testicular echogenicity and presence of microlithiasis contributed in predicting total testosterone and LH values. We derived a new US score, termed TU score, that can predict both impaired spermatogenesis (AUC 0.73, sensitivity 72%, specificity 61%, P < 0.001) and hypogonadism (AUC 0.71, sensitivity 71%, specificity 53%, P < 0.001) more accurately than the Lenz score.

Conclusions: We describe the testicular US characteristics independently associated with impaired spermatogenesis and hypogonadism and propose the TU score as a simple screening method for use in subjects referred for testicular US.