An involuntary male orgasm during sleep is properly called a nocturnal
emission. It is usually referred to as a wet dream.
The testis begin to produce sperm during puberty, although semen
production may well be established before that of sperm making it quite possible
for some boys to ejaculate before they are fertile. The semen and sperm
build up and seek release. If the man or boy does not masturbate or share sex
he is likely to find that ejaculation has taken place while he sleeps.
Many, but by no means all, nocturnal emissions are accompanied by erotic
dreams, passive stimulation by bedding etc or active stimulation during
sleep. Even having a full bladder can trigger a nocturnal emission.
Nocturnal emission is not a sign of any physical or emotional problem. It
is a normal reaction to the body's development. Likewise, the absence
of nocturnal emission is not a sign of any problem, although if an adult male
presented at his doctor's, concerned his testosterone levels may be low, a lifetime
lack of any nocturnal emissions is one of the things that would be likely to be
taken into account.
Although men of all ages experience nocturnal emission, is more common
during puberty than in adulthood, due to both the large surges of testosterone
present in the body during adolescence and the likelihood that a person of
this age is less likely to be releasing semen in other ways.
It is believed that about 85% of men will experience at least one nocturnal
emission during their lifetime. Most nocturnal emissions happen to young men
between twelve and eighteen years of age, tapering off as hormone levels
stabilise and/or masturbation and sharing sex take a more prominent role.