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The Morning Glory (or Nocturnal Penile Tumescence)

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What's the story morning glory?
Well, (you) need a little time to wake up.

- Oasis, UK band

It is common for most sexually able males to wake up in the morning with a substantial erection. By erection we aren't talking about some builders scaffolding or a model of the Eiffel Tower - it is in reference to the erect male member. It goes by many other names - 'woody', 'stiffy', 'hard-on', or 'phwoarr!' - and there have been many scientific (and some not-so-scientific) theories put forward to explain why men suffer1 from a 'morning glory' (also the name of a common flowering plant), but to this date none have been proven. Rest assured though, the occurrence is perfectly natural and nothing to be worried about - unless of course the penis is finding itself erect at the most inopportune moments.

Nocturnal Penile Tumescence

True happiness... arises, in the first place, from the enjoyment of one's self.
- Joseph Addison

The proper scientific name for the early morning erection is 'Nocturnal Penile Tumescence'. Yes, nocturnal means at night, and it's something that is discovered first thing in the morning, but it all starts during sleep, which in general is at night. To delve deeper into the whys and wherefores of the 'early riser' we need to look at some of the philosophies behind the event.

There is the theory of urine retention, meaning the bladder has reached bursting point and with nowhere else to go, urine has filled the urethra, thus engorging the penis. One school of thought says that the penis becomes erect in the morning in order to wake the male to prompt urination. If the sleeping man is laying face down, the discomfort of an erection trying to push its way through to the other side of the mattress can provoke the owner of the penis into action, possibly preventing any accidental bed-wetting.

However, a slight shift in position can resolve any discomfort and the sleeper can continue to dream of fairies, chocolate, jiggly bits, hard-toned bits or other lovely things - depending on sexual orientation. The urine-related theory is perfectly understandable, but is unlikely from a medical or scientific standpoint as the body has many other methods of promoting elimination, particularly as enuresis can affect both sexes.

Others lay the blame firmly on the doorstep of 'wet-dreams' and fantasy, and during such night-time - and sometimes2 daytime - dreams (perhaps connected with REM3), the penis becomes erect in anticipation of sexual intercourse. When rousing from slumber, a man will often find he is 'up for it' - so to speak. This can be either an advantage or disadvantage. Let's look at some of the pros and cons from the male perspective.


  1. On waking, if sharing a bed with a partner, there is an increased likelihood of (and desire for) sex (If partner 'has a headache' - see 2).
  2. On waking, if not sharing a bed with a partner, there is an increased likelihood of (and desire for) masturbation.
  3. If having trouble sleeping, Nocturnal Penile Tumescence followed by post-coital/masturbatory relaxation may help with insomnia.
  4. The erection can be used as a tool during morning chores - hanging a towel from, a place to lay your tie while you button your shirt, or simply something to help you close those lower cupboard doors as you make your breakfast.
  5. Pride. It gets a whole lot bigger when it's erect.


  1. It is wholly embarrassing if you are usually woken in the morning by a female relative, particularly a mother, and you have a rather obvious 'tent' made from your sheets.
  2. If in a hurry to catch a bus or train to get somewhere, it just won't go down, no matter how much you think about cricket, baseball or washing the dishes!
  3. There is a desperate urge to urinate, which can prove very difficult with a semi- or fully-erect penis. This may be one explanation behind the poor aim and handling of the penis that means it invariably leaves puddles everywhere but in the toilet bowl.
  4. After a vasectomy, bouts of Nocturnal Penile Tumescence can make the site more painful.
  5. If you are a sleep-walker, it can be embarrassing when you are seen wandering about the house fast asleep, or worse still, when you wake and find your genitals caught in the closet door for no apparent reason.

Medically Fit for Discharge?

God gave men both a penis and a brain, but unfortunately not enough blood supply to run both at the same time.
- Robin Williams

Through many of his waking hours a male can control his penis (well, some of them can) and so erections are kept at bay. During sleep, however, the body's hormonal and physical control mechanisms for an erection are reduced and, voila, the penis becomes engorged and oxygenated several times during sleep - with some erections lasting as long as two or more hours (according to scientific research4, three to five erections during sleep is average). This is because the penis, like any other tissue in the body, requires oxygenated blood which it gets a substantial amount of during an erection.

Nitric oxide (NO) gas is also an important player in the penis becoming erect. Cells in blood vessel walls release NO, which diffuses into smooth muscle, causing relaxation. However, the result of this is vasodilation, which is an increase in blood vessel diameter. So bigger blood vessels means - well, you get the idea. One of the few cases when NO actually means YES!! The 'morning glory' may be a result of a build up of NO in the body, but this is not conclusive. However, every man should be advised that nitrous oxide (N20) is occasionally used in dental procedures, so a side-effect of inhaling this 'laughing gas' could be excess NO in the bloodstream, possibly resulting in a turgid erection whilst sitting in the dentist's chair!

Half Mast?

In science as in love, too much concentration on technique can often lead to impotence.
- PL Berger

Other than the obvious (steady now...), Nocturnal Penile Tumescence can also be of benefit in determining whether a man is impotent. There are generally two main causes of impotence - psychological or vascular5, both of which can be treated. Don't go jumping off the deep end though if you're male and one morning you wake up with something like an iron bar poking out from your nethers and one morning you don't. The fact is, 'morning wood'6 doesn't occur every morning. And not every week. Or month. But then it can happen two, three, four or even more days in a row!

However, if there is reason to suspect problems with plumbing, doctors can conduct Nocturnal Penile Tumescence (NPT) Monitoring to aid in the detection of possible impotence. A device can be attached to the questionable penis to determine whether it becomes erect during sleep - if indeed the man can get to sleep with a little bit of tape called a snap gauge7 wrapped around his 'John Thomas' over a couple of nights. As psychological interventions are reduced during sleep, a man will often have an erection to oxygenate the penis, ensuring it still receives blood to work. If no erection occurs, it means that the problem of impotence is more than likely vascular, rather than psychological. This can be alleviated through the use of Sildenafil (Viagra), which enhances the effect of NO (nitric oxide) in obtaining an erection, thus encouraging the blood vessels in the penis to enlarge with upstanding results.


Please, sir, I want some more.
- Oliver Twist

Nocturnal Penile Tumescence can give more inches per yard8, so it has greater frequency amongst teenage and younger men as they progress through puberty into manhood. However, that's not to say that men are the only ones who have nocturnal tumescence. Women also require oxygenation of their genitals, so the vagina and clitoris will become stimulated during sleep, just like a man's penis. If you require further information regarding penises and sexual health, there are many services that can help. Don't be shy to talk to a nurse, doctor or other medical professional. Or if you can't face talking, do a little reading up online to allay any concerns.

1If indeed 'suffering' is the correct term.2Sometimes? More like occasional? No, uh - let's just say frequent?3Rapid Eye Movement, the proof that the brain is active during sleep - not the band.4Who funds this research? And where do they get the test subjects from?5Relating to the veins.6A h2g2 Researcher explained this by saying 'I 'would', but I have to get up and go to work.'7Which gets its name from the fact it snaps under pressure. The tape that is, not the penis.8Meaning it can help make the penis bigger.

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