It may be possible to continue to have an erection without testicles. Penile erection is a relatively complex psycho-physiological process. After parasympathetic nerve excitation due to various physiological or psychological stimuli, the small arteries and vascular sinuses in the corpus cavernosum of the penis dilate and blood inflow increases, causing the penis to expand, while the expanded corpus cavernosum compresses the venous blood vessels, decreasing blood outflow and causing the penis to further expand and become erect. If only one testicle is missing and the opposite testicle is normal, an erection is still possible, but if both testicles are missing, an erection is not possible because of the lack of the necessary androgens. The testicle is a sex organ that produces sex hormones as well as androgens, and the absence of a testicle may lead to conditions such as decreased libido. The absence of testicles must be taken seriously, go to the hospital for further examination, and follow the doctor’s instructions for treatment.