Tri-7 Wk12, Days 440 - Monday

Looking back at my last blog I noticed we had a freak burst of snow on Friday and it looks like we're getting more snow tonight ...after an absolutely gorgeous & warm day today. Gotta make this quick - only got an hour of sleep last night but I do know tons more about diabetes insipidus - I guess we can start there.

There's Diabetes Mellitus (DM) and Diabetes Insipidus (DI). DM seems to be the more popular of the two diabetes and with DM we have Type I and Type II. Type one is the kind where the beta cells in the pancreas just aren't able to do their job of creating insulin very well anymore and with Type II we might have the insulin available but the receptor sites just aren't so receptive anymore.

With DI, instead of talking about insulin, we're talking about ADH, Anti-diuretic Hormone which also goes by it's more scientific name of arginine vasopressin or AVP or, more simply vasopressin. ADH helps a person regulate (and retain) water when necessary. If you're in the dessert, you'll be happy to have ADH. Keep in mind, a diuretic makes you pee so ...an anti-diuretic is going to prevent that from happening.

With DI we have four major types but, like a lot of disease type situations, on one side of the spectrum we have the necessary element (in this case ADH) not being made and on the other end of the spectrum the ADH isn't being very well received.

Off the top of my head, I'm thinking of a bakery that delivers it's goods to stores to be sold. If you run out of flour at the bakery then you can't produce the goods and soon the stores shelves will be empty. If you can make the goods but the store employees are on strike then the store will be closed and the goods won't be sold.

In the first type of DI, we have Neurogenic Diabetes Insipidus, sometimes called Central Diabetes Insipidus (CDI). CDI most often is the result of trauma to the brain either from an accident or as a result of brain surgery. Incidently, in case you didn't know, ADH is made in the pituitary region of the brain. And, for those that do know and what more detail ...about 5/6th of the bodys ADH is made in supra-optic nucleus and 1/6th is made in the paraventricular nucleus then the ADH travels down the hypothalamic tract into the neurohypophysis where it meets up with the inferior hypophysial artery

so ...like I said, ADH is made the brain and if there's damage to the area where ADH is made then we mess up production and end up with Neurogenic Diabetes Insipidus.

That means no ADH and our patient will end up excreting very large amounts of hypotonic, insipid (tasteless) urine. This condition is usually caused by polyuria (increased urination) and polydipsia (increased thirst) not a cool situation.

OK. Neurogenic is one. When you see the Neuro in neurogenic think of the head.

Nephrogenic Diabetes insipidus is the 2nd type of DI on our list. When you see the "nephro" in nephrogenic think of Nephrons which should make you think of kidneys. You guessed it, nephrogenic DI is a problem on the receiving end of this manufacturing process.

Now, there are places like your sweat glands and small arteries which like to receive ADH but, the kidneys are like the Wal-Mart of receiving when it comes to ADH - the big dog. And, if the kidneys aren't happy - aint nobody gonna be happy. If ADH can't hit it's primary target of the kidneys then it's going to be a lot like if the ADH wasn't there to begin with ...so, we once again have the polyuria (increased urination) and polydipsia (increased thirst)

some reasons for the kidneys being all pissy towards ADH include things like chronic renal insufficiency, lithium toxicity, hypercalcemia, hypokalemia, etc

but ...what if you're born with it?

I once remember reading about the V2 rocket developed over in Germany. With the kidneys, we're talking about a V2 receptor that likes to play nice with ADH. *Usually* likes to play nice and, when the V2 receptor is built correctly, it does play nice.

But, the gene that has the blueprint for making V2 receptors is carried on the X chromosome and sometimes the instructions are messed up and bad V2 receptors are built.

Boys have an X and a Y chromosome - it's what makes them boys. XY

Girls have two X chromosomes, it's what makes them girls. XX

If you're a boy and you have bad instructions for building the V2 receptor then you're kind of screwed because you only have one X to rely upon.

If you're a girl and have bad instructions on one of your X chromosomes ...well, you're in luck because you happen to have a second X chromosome which will probably have to correct instructions for building V2 receptors! :)

So, you'll see this form of Diabetes Insipidus more often with boys since girls get that extra chance of making things right.

Of course, theres more to it than just receiving. Just because the truck backs up to the warehouse door doesn't do much good if it just sits there.

So, V2 is the welcoming committee for ADH but then we need a little something called "aquaporin 2" and, that comes from the aquaporin-2 gene, of course. That gene has the instructions for building aquaporin 2. That gene makes the kidneys water channels so that water can be re-absorbed.

But, what if there are bad instructions for making aquaporin 2? Those instructions are not carried on the X or Y gene so it's an equal opportunity gene and, if it's bad may affect either gender.

Both parents will have to have a bad set of instructions for making aquaporin 2 in order for the offspring to get screwed which, tends to make this cause of nephrogenic DI more rare than the V2 congenital kind.

I've gotta get to bed ..pushing 10 p.m. ....

Gestational DI is a third type of DI. We're talking about pregnant ladies with this one and ...let's just get it out there - it involves having elevated levels of placental cystine aminopeptidase! Yeah, you heard me.

hmm. that long, confusing word ends with the letters -ase. So, we must be talking about an enzyme, right? Right.

we could also call it vasopressinase. so, basically vasopressinase eats up all the vasopressin and, once again, we're left without any vasopressin (ADH) in the system

Dispogenic DI is the last type and this involves primary polydipsia - drinking WAY too much. So much that there really isn't a need for an antidiuretic hormone because there's no need to be conserving water. This can cause other issues though. there isn't a standard treatment for the dispogenic variety of DI but, sometimes it's caused by a mental illness so, if the mental illness can be fixed then the dispogenic DI might get fixed as well.

Today's picture is of Koilonychia or a "spoon-shaped" nail. not having enough iron in your body is typically the cause of koilonychia which, has nothing to do with diabetes insipidus but, i thought I was going to be talking about bochdalek hernias and things like that which is what we talked about today in class but I got carried away with DI so those other fun things will have to wait. :)