It is interesting to observe that low testosterone exhibits opposing erection phenomena in the general population of men vs men with SCD: while low testosterone may contribute to decreased erection in the general population having cardiovascular or metabolic factors affecting erectile tissue function, it results in uncontrolled erection in the SCD population, which has a severely disturbed PDE5 regulatory pathway in the penis. Here, PDE5A is linked to Schnyder corneal dystrophy.