Thyroid UK
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Orexin - ever heard of this hormone?

I have trouble falling asleep but my worst prob is waking up at 4:45 am when I'd rather wake up an hour or more later. I read an article that Orexin regulates sleep and hystmine release. Does anyone have experience or knowledge of Orexin? ( FYI - I'm being tested to see if cortisol or thyroid are the culprits too. I get the test results next week).

2 Replies

I quote from Wikipedia:

There are two types of orexin: orexin-A and -B (hypocretin-1 and -2). They are excitatory neuropeptides with approximately 50% sequence identity, produced by cleavage of a single precursor protein. Orexin-A is 33 amino acid residues long and has two intrachain disulfide bonds; orexin-B is a linear 28 amino acid residue peptide. Studies suggest that orexin-A may be of greater biological importance than orexin-B.[citation needed] Although these peptides are produced by a very small population of cells in the lateral and posterior hypothalamus, they send projections throughout the brain.

The orexins are strongly conserved peptides, found in all major classes of vertebrates.

The orexin system was initially suggested to be primarily involved in the stimulation of food intake, based on the finding that central administration of orexin-A and -B increased food intake. In addition, it stimulates wakefulness, regulates energy expenditure, and modulates visceral function.


I've never heard of Orexin. It's name immediately suggested something to do with eating as in anorexia and in Greek bon appetit is kali orexi. It certainly is involved in appetite among other things. I also tend to wake up too early and now I think it might be to do with falling oestrogen levels. Oestrogen seems to inhibit orexin according to this article So if someone is menopausal or post menopause this could explain poor sleep.

Trouble falling asleep might be due to low levels of melatonin. I also have trouble falling asleep! I have read that tart/sour cherries have melatonin and seem to help with getting better sleep. Cherry Active produce tart cherry juice concentrate which is the next best thing to taking melatonin which is not approved in the UK.


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