Probably from all the excitement about the report yesterday in the journal Science explaining why little dogs are little and big dogs are big, I forgot to mention a couple of things in my posting about the report. First, do you know why pigmies are short? It could be that they have the IGF-1 suppressor gene just like the little dogs.  Actually, they don’t; in the pigmies, the “problem” (I suspect the pigmies don’t consider their short stature a problem, just the normal state of affairs) is failure to respond to the IGF-1/IGFBP3 complex- they just don’t generate whatever growth factors are normally stimulated by the IGF-1/IGF-1BP3.  Just another example of what I mentioned yesterday- in nature, generally whatever can go wrong will do so sometimes.  Of course, we should be thankful that most of the time, things work just fine.

One other thing- treating people (or dogs) with IGF-1. I forgot to mention that IGF-1 must be injected, it’s very expensive,  and it causes hypoglycemia (low blood glucose levels).  Thus, treatment with IGF-1 has medical and financial risks.  The reason it causes hypoglycemia is that the structure of IGF-1 is very similar to the precursor molecule to insulin, proinsulin.  Thus, the IGF-1 acts like insulin in some ways.  I think that’s pretty interesting.