**Core Concept**
Conn's syndrome, also known as primary aldosteronism, is a condition characterized by excessive production of aldosterone, a hormone that regulates electrolyte and fluid balance in the body. The primary pathophysiological mechanism involves an overproduction of aldosterone, leading to sodium retention, potassium excretion, and subsequent hypertension.

**Why the Correct Answer is Right**
In Conn's syndrome, the increased levels of aldosterone cause sodium and water retention, leading to hypertension. However, the body's compensatory mechanisms, such as increased renin and angiotensin II, help maintain a relatively normal blood volume, thereby preventing edema. Additionally, the increased potassium excretion can lead to hypokalemia, which further contributes to the development of hypertension.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because Conn's syndrome is characterized by excessive aldosterone production, which leads to hypertension, not hypotension.
**Option B:** This option is incorrect because while Conn's syndrome is associated with hypertension, it is not the primary cause of diastolic hypertension without edema.
**Option C:** This option is incorrect because Conn's syndrome is primarily caused by an adrenal gland disorder, not a renal disease.

**Clinical Pearl / High-Yield Fact**
A key clinical clue for diagnosing Conn's syndrome is the presence of hypokalemia, which is often accompanied by hypertension and suppressed plasma renin activity.

**Correct Answer:** C.