When the effects of androgens in the body are lessened, e.g. through lowering DHT or by systemic hormone receptor blockade, the body seeks equilibrium through a process called upregulation. This can take the form of increased hormone production and/or increased tissue sensitivity to the remaining hormones.

The reason side effects usually gradually disappear with finasteride is probably due to such upregulation. In a small percentage of individuals, it may be that this process overshoots the mark, resulting in significant hyperandrogenicity.

This is marked by such signs as greatly increased facial oil, increased pimples, and greatly elevated libido. It's possible that in certain cases such hyperandrogenicity overcomes the hair-protective effect of, say, finasteride, though this does not appear to be the case for the vast majority of people..