Can masturbation really causes shrinkage of the penis?

No Evidence. Masturbation does not cause reduction in penile size. As men age, however, there may be a perceptible change in penis size when flaccid. This can occur from diminishing blood flow at rest.. The erectile tissue, if not periodically stretched by full filling, can result in diminished size of the erection. This has been demonstrated in animal studies and in men whom have had their prostate removed.