probably the most frequent cause of small testicles is klinefelter syndrome ( xxy/47 ) , involving a wide spectrum from eunuchoid hypogonadism to a normally virilized albeit sterile male , in whom gynecomastia is not much more frequent than in the average male population but in whom the mammary cancer risk is definitely elevated almost to female rates .
C0022735
klinefelter syndrome
C0020619
hypogonadism