**Core Concept**
Diuretics are a class of medications used to treat hypertension and edema by promoting the excretion of excess fluids and electrolytes from the body. However, certain diuretics can have significant side effects, including erectile dysfunction (ED).

**Why the Correct Answer is Right**
Erectile dysfunction is often caused by decreased blood flow to the penis. Thiazide diuretics, particularly those with a high potency, can lead to ED by causing vascular smooth muscle relaxation and decreased blood flow. This is due to their mechanism of action, which involves inhibiting sodium reabsorption in the distal convoluted tubule and increasing sodium excretion in the urine. As a result, there is a decrease in the calcium reabsorption, leading to increased levels of calcium in the urine, and subsequently, decreased blood flow to the penis.

**Why Each Wrong Option is Incorrect**
**Option A:** Loop diuretics, such as furosemide, can lead to hypokalemia and metabolic alkalosis but are not commonly associated with erectile dysfunction.
**Option B:** Potassium-sparing diuretics, such as spironolactone, can cause hyperkalemia and gynecomastia in males but are not typically linked to ED.
**Option C:** Osmotic diuretics, like mannitol, are used to reduce intracranial pressure and are not commonly associated with ED.

**Clinical Pearl / High-Yield Fact**
When prescribing diuretics, it's essential to consider their potential side effects, including erectile dysfunction, especially in patients with a history of hypertension or cardiovascular disease.

**Correct Answer:** C.