Which of the following conditions is known for causing impotence due to reduced blood flow?

The correct answer is Lerich syndrome, which is characterized by aortoiliac occlusive disease leading to reduced blood flow to the pelvis and lower extremities. This reduced blood flow can directly impact erectile function, as adequate vascular supply is essential for achieving and maintaining an erection. In Lerich syndrome, blockage in the main arteries that supply blood to the groin and pelvic region can result in erectile dysfunction due to the ischemia experienced by the erectile tissues.

While other conditions like diabetes mellitus and hypertension can also contribute to erectile dysfunction, primarily through mechanisms like nerve damage or impaired vascular function, Lerich syndrome uniquely highlights the issue of reduced blood flow due to major arterial blockage directly affecting the area responsible for erections. Diabetes mellitus often leads to both vascular and nerve complications, while hypertension may lead to erectile difficulties primarily through its effects on vascular health and the medications used to treat it. Peripheral neuropathy, often associated with diabetes, can affect nerve innervation but does not specifically indicate reduced blood flow as a primary cause of impotence.