Ah, morning wood - frequently the first friend a man sees when he wakes up in the morning. That erect penis that greets so many men at the start of the day is so familiar that most of us take it for granted.
A guy barely gives it a thought (although he may occasionally give it a few tugs when he has the time), but that morning wood can tell a man a lot about his penis health - and even something about his overall health as well.
Why an erect penis in the morning?
So waking up with an erect penis is common - but why should it be? What is it about sleeping that causes morning wood? To understand that, it's necessary to first understand the whole erection process.
The process
Clearly, a man's penis becomes erect in order to facilitate sexual activity. Without a suitable erection, intercourse, oral sex, masturbation or any other form of sex is not possible.
Most of the time, erection occurs as a result of arousal. That means a man receives some form of sensory input - a pheromone scent, a visual that creates sex appeal, a manual stimulation of the organ, etc. - that the brain interprets as pleasurable.
It responds by telling the body to release chemicals that cause the penis to become engorged with blood. The strength of the sensory input (and the health functioning of the penis) will determine how firm the penis becomes and how long it stays firm.
During the waking hours, men get erections when they see someone wearing revealing clothing or hear someone speaking in a sultry voice. But they may also get erections for no apparent reason. Often this is due to the spinal cord releasing the chemicals that bring about a reaction at random intervals.
Morning
So why is a man waking up erect? Because during sleep, a person goes through several cycles of what is called REM (rapid eye movement) and non-REM sleep.
During the phases of REM sleep, the brain is likely to release the chemicals responsible for arousal. And most of the time when a man wakes up, he is coming out of an REM phase - and hence is more likely to sport a bit of morning wood.
In some instances, a man may wake up with an erection because he has a need to urinate and the sleeping body responds to that by forming an erection, which makes it less likely that the man will urinate while sleeping.
Health indicator
It's generally a good sign to wake up with an erect penis. It's clearly a sign that things are functioning well, that the penis is capable of achieving erections and that there is no reason to assume serious tissue damage or other penis health issues.
And by increasing oxygen flow to the penis (through the increased flow of blood), the nocturnal and morning erections help to maintain that health.
What about men who don't regularly wake up with an erection? It may be a sign of erectile dysfunction and/or low testosterone levels. It may also indicate some other health issues. For example, lack of regular, firm erections may indicate some cardiac or blood pressure issues.
Diabetes can also affect erectile activity, as can depression (even when asleep). So men who do not find themselves with morning wood on a fairly regular basis may want to check with a doctor for other possible concerns.