That's the thing, creatine is not *really* thoroughly researched yet and we are still finding things out. Most studies only show a loading phase followed by a maintenance phase but fail to test consistently a wide range of factors. Then there are studies like this one that fly under the radar:
Creatine supplementation increases glycogen ... [Clin Sci (Lond). 2004] - PubMed - NCBI
Essentially, loading with 20g a day creatine skyrocketed creatine levels and muscle glycogen levels. As far as I am aware there are no studies that show creatine use with high dose over more than 7 days. The maintenance dose failed to maintain the high creatine and muscle glycogen levels. I would really like to see what 60g a day would do over day 20 days- I might try it myself soon actually and document the results here.
Creatine will also increase the conversion of testosterone to DHT significantly and this *possibly* may be another mechanism of action.
Three weeks of creatine monohydrate supplem... [Clin J Sport Med. 2009] - PubMed - NCBI
Then there is evidence that creatine is incredibly anti-catabolic and even works as a myostatin inhibitor
Effects of resistance exercise with and witho... [J Appl Physiol. 2008] - PubMed - NCBI (free full text)
Another thing it does in HIGH doses is increase the levels of GLUT-4 that come out of the muscle cells during resistance training. This means that for about ~1 hour afterwards your muscles will soak up more carbs than without creatine. Combine this with a post workout shake of loads of sugar, leucine and hydrolysed protein and the whole lot will enter the muscles before insulin even has a chance to tell the GLUT-4 in your fat cells to soak up the carbs you just drank (you literally don't get fat if you down it in that hour and high creatine levels will increase the amount of sugar you'll be able to take in)
Effect of oral creatine supplementation on human mu... [Diabetes. 2001] - PubMed - NCBI - also one other study above shows this
It sounds like I'm going on or trying to make a silly point but I really do not see why creatine supplementation should be allowed with WADA tested athletes- especially when drugs such as cannabis are banned. I would commend anyone that can eat enough red meat to get 30g a day of creatine because that is pretty much 5kg of beef a day we are talking about. I'm just dumping info on creatine now I'm not especially trying to argue here (I know people have the incredible ability on the internet to read things in the most offensive way possible but that is not what I am trying to do)
Creatine will ALSO cause increased insulin resistance in the very short term after taking it- so if you're a morning trainer and like to eat afterwards you don't need to worry about insulin sensitivity early in the morning and fat gain if you take it first thing
Regarding IGF, I don't think that should be allowed despite it being in milk. It has a functional half life in the body of under an hour- if anyone would want to pin themselves every hour then congratulations lol, you want to win more than I do. There are other forms of IGF that are gene spliced to have longer half lives (up to 30h with IGF-1 LR3) but alas, this is not found in food