A hard penis in the morning is a man’s morning erection, mainly due to the process of sleep at night, due to parasympathetic excitation and sympathetic inhibition, so it will cause vasodilation of the penis, which will increase the blood supply to the arteries. So sleeping at night or in the morning will cause the penis to be in an erect state. Under normal circumstances, the frequency of penile erection at night is about 4-6 times, and the duration of each time is about 20 minutes, which is a normal physiological phenomenon. So many men wake up in the morning and find that their penis is in an erect state, but for patients with certain diseases, the morning erection usually disappears. For example, the presence of a vascular malformation of the penis or the presence of chronic lesions that cause narrowing of the blood vessels in the penis can cause a weak or absent morning erection. If the morning erection does not exist, it often indicates the presence of some disease that causes impotence.