Ultrasound and 18F-FDG PET evaluation of age-related testicular volumetric and metabolic changes during andropause

Abstract

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Objectives: Many studies have reported clinical symptom and male hormonal changes during andropause. However, unlike menopause, there is no clear description of age-related changes in testicular volume and metabolism during andropause. The aim of this investigation is to evaluate volumetric and metabolic changes of the testicles with ultrasound and FDG-PET imaging around this age stage. Methods: This retrospective study included a total of 163 men (age range, 40-90 years) with normal testicles; 109 subjects had whole-body 18F-FDG PET and 54 subjects had genital ultrasound. The subjects who had a history of pelvic metastasis, prior chemotherapy or pelvic radiation therapy, and testicular inflammation and infection were excluded. Maximal standard uptake values (SUVmax) and volumes of the testicles were examined at each decade in each subject. An average SUVmax and average volume of both sides were used for a regression analysis. Results: Above age 40, both testicular volume and SUVmax tended to decline with increasing age with significant negative correlations (volume: r = -0.5; SUVmax: r = -0.44). The regression analysis demonstrated that after age 70, the rate of volumetric decrease became more rapid, although the rate of decline of SUVmax remained constant (see figure below). At age 40, 60, 75 and 90, the testicular volume was noted 16.8, 14.8, 12.6 and 4.6 cm3, and SUVmax was noted 2.3, 2.1, 1.8 and 1.7, respectively. Conclusions: This preliminary data demonstrates a decline in normal testicular volume and metabolism in adults that is significantly correlated with increasing age. In elderly adults, a relatively more rapid decrease in testicular volume was noted after age 70 but without a change in the rate of decreasing metabolism.