Video Transcript
Some tumors of the pancreas called
insulinomas make excessive amounts of insulin. What could be the consequence of
too much insulin in the body? (A) It makes the liver store
glucose. (B) Blood glucose drops too
low. Or (C) blood glucose becomes too
high.
This question is asking about
insulin, a hormone produced by the pancreas. To answer this question, let’s
review the key facts about the endocrine function of the pancreas and how the
hormones it produces help to maintain the level of glucose in the blood within a
healthy range. Otherwise, it can be dangerous.
To talk like a biologist, we can
say that the pancreatic hormones are involved in the homeostasis of blood
glucose. But how does this work? The pancreas produces two hormones:
insulin and glucagon. These work antagonistically, which
means they work against each other. When we consume carbohydrates in
our food, they are broken down into their most basic building blocks,
monosaccharides. The most common one of these is
glucose. Monosaccharides are small, soluble
molecules, which means they can be absorbed from the small intestine into the
blood. They then quickly circulate in the
blood, as you can see represented in this diagram by the little green dots in the
blood vessel.
The blood glucose levels therefore
rise. This rise is detected by the
pancreas, which responds by secreting insulin into the blood. The insulin is then carried all
around the body, and it stimulates most of the body’s cells to absorb glucose
immediately. When the insulin reaches the liver
and muscle cells, it stimulates them to absorb the glucose and then join these
glucose molecules up to form glycogen. Glycogen is a large, branched,
insoluble carbohydrate, which is unreactive. These features make it an ideal
storage carbohydrate, which can sit inside the cell until it is needed.
We can now rule out answer option
(A) as we now know that although insulin makes liver cells take up glucose from the
blood, this glucose is actually converted into glycogen to be stored.
The uptake of glucose by all the
cells brings the blood glucose levels back into the normal range. But what happens when we now use
this glucose and the blood glucose levels drop? When blood glucose levels fall, the
pancreas releases a hormone called glucagon into the blood. The glucagon is carried all around
the body in the bloodstream. When it reaches the liver cells, it
signals to them to break down their stored glycogen to release glucose back into the
blood. This then brings the blood glucose
levels back up within the normal range.
Now that we have a better idea of
what happens in glucose homeostasis, let’s try to imagine the effect of the
insulinomas mentioned in the question. The question tells us that
insulinomas are tumors of the pancreas that make excessive amounts of insulin. We can presume that this will
stimulate the body cells to absorb more glucose than they need to, leaving less
glucose in the blood. This results in hypoglycemia, or
low blood glucose, hypo- meaning low and glycemia referring to glucose. The body cannot function properly
in this state, and the person can experience blurred vision, feeling very weak, and
can even faint.
Having reviewed the key facts about
the endocrine role of the pancreas and thought through the effect of high insulin
levels on the body, let’s return to the question. We now know that the correct answer
to the question is option (B). The consequence of too much insulin
in the body is that the blood glucose drops too low.
