Hello and welcome to the Zero to Finals podcast. My name is Tom and in this episode I'm going to be talking to you about syndrome of inappropriate antidiarratic hormone, also known as S-I-A-D-H.

If you want to follow along with written notes on this topic, you can follow along at zero definals.com slash

s IADH or in the endocrinology section of the zero to finals medicine book.

Let's start with some basic pathophysiology of SIADH.

Anti-diuretic hormone is produced by the hypothalamus and secreted by the posterior pituitary gland.

It's also known as vasopressin and the job of ADH is to stimulate water reabsorption from the

collecting ducts in the kidneys. So it takes water out of the urine in the collecting ducts

and puts it back into the blood.

S-I-A-D-H is a condition where there's inappropriately large amounts of ADHD hormone,

and this may be the result of the posterior pituitary gland secreting too much ADHD,

or the ADHD coming from somewhere else, for example, a small cell lung cancer. The excessive ADH results in excessive water reabsorption from the collecting ducks in the kidneys,

and this dilutes the sodium in the blood, so you end up with a low sodium concentration,

which we call a hyponotremia.

The excessive water reabsorption is not usually significant enough to cause a fluid overload,

so you end up with something called a eovelymic hyponotremia, where their fluid balance is normal,

but their sodium concentration has been diluted, and they have a hyponotremia.

The urine becomes more concentrated, as less water is being excreted by the kidneys. So patients with S-I-A-D-H have a high urine osmalality

and a high urine sodium. So what are the symptoms of S-I-A-D-H? Well the symptoms relate to having a hyponetremia and they're quite

nonspecific so it's things like headache fatigue muscle aches and cramps and in severe hyponetremia

you can have confusion seizures and reduce consciousness. S-I-A-D-H has countless causes.

Some of the key causes that you'll come across are post-operative.

So if they have major surgery, quite often people get at S-I-A-D-H post-up.

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