Every morning when you get up the lower side are hard that male sexual function is normal, male patients during the day mainly by sympathetic innervation, parasympathetic nerves are in a state of inhibition, the penis is weak during the day; night is mainly parasympathetic innervation, male penis will have four to five erections at night, each erection lasts for a different three minutes to half an hour ranging. Men get up in the morning and find that the penis is very hard, is a normal physiological reaction of men is not a lesion do not worry, many people go to bed at night before the penis erection is not particularly obvious, wake up in the morning penis erection obvious can try to have sexual intercourse at this time.