How does age affect the testicular volumetric and metabolic changes?

Abstract

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Objectives: Better understanding of normal testicular volumetric and metabolic changes with age is essential to differentiate pathology from physiologic changes due to age in the clinical setting. The aim of this investigation is to evaluate the effect of age on testicular volume and metabolism using ultrasonography (US) and FDG-PET imaging. Methods: This retrospective study included 287 male subjects with normal testicles (age range 11-90) who underwent whole-body 18F-FDG PET scan or testicular US study during Jan. 2003-Nov. 2006. Subjects who had a history of pelvic metastasis, previous chemotherapy or pelvic radiation therapy, and testicular inflammation and infection were excluded. Volumes and maximal standard uptake values (SUVmax) of the testicles were recorded at each decade. Average volumes and average SUVmax of both sides were used for a polynomial regression analysis. Results: Polynomial regression curves demonstrated the change in testicular volume and SUVmax significantly correlated to increasing age from 11 to 90 (volume: R2=0.396 p=0.004; SUVmax: R2=0.298, p=0.0004). Changes in volume first showed a linear increasing phase from 11 to 35 years of age (r=0.58, p<0.0001), reached a peak at about age 35, then a relative plateau phase with slightly decreasing volumes during the ages of 36-69 (r= -0.148, p=NS), with a subsequent more rapid decline phase after age of 70 (r= -0.58, p=0.003). However, change in SUVmax first showed a linear increasing phase from the age of 11 to 40 (r= 0.68, p=0.005) with a peak at approximately age 40, followed by a gradual decline without rapid decrease by age of 90 (r= -0.44, p=0.005). Conclusions: Testicular volume and metabolism were significantly affected by increasing age with different rates of changes at different stages of life.