What comes to connective tissues, calcium, D3, Biotin etc. deal with some of that at least. And growth hormone, there's of course L-tyrosine, GABA, L-carnitine + L-ornithine combo and so on. But MSM has quite unique properties, its also extremely cheap. I get mine from a shop who are selling supplements for pets. Several of their products have a mention "this substance has other uses but we wont discuss it here." Which is pecualir, I bet they're selling the stuff to people and get them cheaper as they're for pets and thus going around bunch of bureaucracy and extra costs.