A hard penis is a form of erectile dysfunction, which may be due to age factors, as well as mental factors, bad habits, and chronic diseases of the body. 1. Age factor: with age, the level of androgen in the body decreases, which may affect penile erection and lead to erectile dysfunction. 2. Mental factors: mental stress, burden of thought, or a history of poor sex life, as well as the emotional factors of the couple, may affect penile erection, resulting in erectile dysfunction. 3. Bad habits: for example, regular smoking, alcoholism, staying up late, and irregular lifestyle may also cause erectile dysfunction. 4. Chronic physical diseases: for example, chronic cardiovascular diseases, hypertension, diabetes, chronic tumors and other diseases can also cause erectile dysfunction. Erectile dysfunction may also be caused by other factors, you should go to the regular hospital in time to check, follow the doctor’s instructions for treatment, and strive for early recovery.