I've had a lot of testicular atrophy, however, I can't say how much of that is actual reduction in testicle size and how much of it is due to the fluid around my testicles that remained after a badly done hydrocele repair having gone away - either way I'd say I've had somewhere between a 50%-75% reduction in overall size. As far as my penis is concerned, it seems that it has permanently gone in to 'cold weather mode' rather than had any real reduction in size - so it appears to be smaller, but I'm not convinced it really is.