Question:
People who do not have diabetes rarely have low blood sugar levels. Why is
this? When they do border on a low level what causes it to go back up? I
thought diabetes was just the lack of a functioning insulin producing pancreas
- meaning that you need manual injections to lower your blood sugar level. So
why is it that diabetes also causes your blood levels to drop dangeroulsly low
even when you're not taking insulin and just exercising?
Answer:
The main reason a non-injecting T2 would go low, other than certain
medications, is that in T2 the beta cells in the pancreas often get their
timing screwed up and instead of releasing large amounts of insulin the
moment the blood sugar starts to rise ("Phase I response"), they do it a
couple hours late. The result is that the blood sugar goes too high,
eventually starts to come down (too slowly) due to uptake from the
muscles, and then drops suddenly as a result of the delayed pancreatic
response. At this point the alpha cells in the pancreas detect this drop
and release glucagon, which causes the liver to release glucose into the
blood by two different mechanisms. This takes some time to kick in, so
the person will experience hypo symptoms in the meantime and will probably
treat them by consuming some carbohydrate. This brings the glucose back
up to normal, but then the liver pull-up brings it too high (and another
common problem in T2s is that the liver doesn't know when to stop).
In technical terms, what you have is a feedback control system that's
gone into oscillation because of an excessive phase shift around the loop.
Instead of holding the blood glucose nearly constant, the system swings it
up and down wildly. The end result is that you wind up running both high
blood glucose levels *and* high insulin levels. This in turns messes up
your lipid metabolism, which damages your blood vessels *and* screws up
the beta cells even more. There are several vicious circles involved.
This, BTW, is why people with reactive hypoglycemia often progress to
diabetes, and why the treatments for the two seemingly opposite conditions
are so similar. The main method of attack is to limit the amount of
carbohydrates consumed at any one time so as to limit the immediate
postprandial rise, which in turn limits the exaggerated insulin response.
