Epidemiological curves relating IGF levels to mortality are often U-shaped, down-sloped, or flat.

“so igf is kind of the biomarker for this action igf itself is really complicated because there are five actually i hear that there are seven binding proteins and there's a lot of regulation in between but it's true to say that high i that levels of igf are really very good biomarkers even if you don't agree that they're causative for variety of of health outcomes”

“but the story seems much more complicated than igf is bad i agree and again i think you know going back to the the levine paper that we were talking about again i think it's a it's an important paper it's a well-done paper you really have to recognize that um the population you're looking in might make a big difference as well right so we you know if you're talking about a population of people where 30 of them are obese some high percentage have metabolic disease or diabetes you know having high igf-1 in that context might be very different than somebody who is sensitive exercising eating a high protein diet right and again that those kinds of things don't typically come out in these epidemiological studies”