This is a completely legitimate and rational fear that disrupts a man’s ability to become aroused. If a man is not ready for a child and you are not on birth control, there is always a chance you could conceive. If you are new to one another, he doesn’t know for certain if you are a carrier of a disease. This is where the physiological and the psychological partner up and shut it down, to protect their dude.
NO is produced by the enzyme NO synthase (NOS).  NOS plays many roles, ranging from homeostasis to immune system regulation. To date, 3 subtypes have been identified: nNOS, iNOS, and eNOS, which are produced by the genes NOS1, NOS2, and NOS3, respectively. This nomenclature is derived from the sources of the original isolates: neuronal tissue (nNOS), immunoactivated macrophage cell lines (iNOS), and vascular endothelium (eNOS). The subtypes are not, however, limited to the tissues from which they were first isolated.
Men who wear tight underwear may also experience the same problems. Because of the constriction, feeling may be lost, and even if unnoticed actively, the brain will notice. This is part of the complication with erectile dysfunction between the brain and the body. While you may be in the mood, if the proper electrical signals are not sent back and forth, nothing will happen.
An approach to the diagnosis and management of the impotent patient is presented in Figure 187.1. Apparent and likely causes of impotence should be considered first and, if possible, eliminated before the work-up continues. For instance, observing the patient for a few weeks off offending medication may be all that is necessary to establish the cause of impotence. When no obvious or remediable cause is present, the next step is based on the clinical impression of the likelihood of organic versus psychologic impotence. If the latter is considered more likely, it is perfectly reasonable to refer the patient directly for sexual therapy, with the option of reconsidering the diagnosis if, after appropriate therapy, there is no improvement. While an occasional patient with organic impotence will be misrouted, many more with psychogenic impotence will be spared an unnecessary and costly evaluation for organic causes. When organic impotence is likely, a serum testosterone level is the initial screening test for hypogonadism and should be obtained prior to urologic referral. Patients with low testosterone levels require further endocrine evaluations as depicted in Figure 187.1.
Having erection trouble from time to time isn't necessarily a cause for concern. If erectile dysfunction is an ongoing issue, however, it can cause stress, affect your self-confidence and contribute to relationship problems. Problems getting or keeping an erection can also be a sign of an underlying health condition that needs treatment and a risk factor for heart disease.