How does Finasteride work on the hair?

Does finasteride only prevent more terminal hairs from miniaturizing? Does it thicken existing miniaturized hairs? Does it help regrow hairs from follicles that stopped growing?  

Terminal hairs do not respond in any way to finasteride. It does thicken existing miniaturized hairs and may induce hairs that have failed to regrow if it is recent hair loss. Finasteride works by blocking the hormone DHT, which prevents the genes from kicking in to cause the loss in men that have the genes for hair loss.