[rosy (OP)]

Am I right in thinking that it's the antidieuretic (sp?) hormone (ADH) that your body produces more of at night to help prevent you having to get up and pee at regular intervals?
Is there some other hormone that triggers this extra ADH? A few years ago (6 or 8 years ago, I think) I knew a child who was being prescribed some kind of hormone tablet to allow them to go to sleepover parties etc without embarrasment... but it wasn't the sort of thing I was going to quiz an 8 year old about! So now I'm curious... anyone know anything?
Will how much you produce depend on how deeply asleep you are?
(Of vague relevance to a discussion in this thread:
http://www.thenakedscientists.com/forum/topic.asp?TOPIC_ID=1982&whichpage=5 )

[chris]

ADH, which is also known as AVP or arginine vasopressin, is a peptide (protein) hormone consisting of 9 amino acids which locks on to surface docking sites, called V1 and V2 receptors, on ADH-responsive cells in the kidney and blood vessels. V1 receptors are found on blood vessel muscle cells, whilst V2 receptors are found in the kidney.

When ADH binds to V2 receptors it triggers the production of a cellular messenger called cAMP which opens a series of 'water channels' in the collecting ducts, leading to increased water resorption from urine.

ADH is released by the pituitary gland in the brain under instructions from the hypothalamus above it. The hypothalamus is involved in controlling various bodily functions including 'circadian rhythms' - the natural day-night fluctuation in hormone levels. When we sleep the hypothalamus increases the production of ADH to cut down urine output. However, there are limits to this adaptive response and if you drink 5 pints of lager before bed you can still expect to wake up wanting a pee !

Chris

ADH also works as a vaso-constrictor (causing blood vessels to close) and hence increases blood pressure. This is an appropriate reaction since water-depleted individuals may be vascularly underfilled and prone to low blood pressure.

There are a few drugs that can mimic the actions of ADH including desmopressin and felypressin. Desmopressin boosts kidney water reabsorption and therefore cuts down urine production.

Chris

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