The decline in HP is not permanent. This is according to Per's guide, which seems to be down at the moment. Fortunately I have a copy on local disk... Anyway, there is a persistent rumor (both in and out of game, oddly enough) that the toe can be used on the end boss. Unfortunately it does the same thing to you him as it does to you; that is reduce your max HP by 3. Supposedly you could repeat the toe process 333 times to get enough to whittle away his 999 hit points... but that would be... odd to say the least.