Which of the following conditions is characterized by episodic headaches, sweating, and tachycardia?

The condition characterized by episodic headaches, sweating, and tachycardia is pheochromocytoma. This is a tumor that arises from the adrenal glands and results in excessive production of catecholamines, such as epinephrine and norepinephrine. These hormones are responsible for the body's "fight or flight" response, causing symptoms like increased heart rate (tachycardia), episodes of headaches due to increased blood pressure, and excessive sweating. The hallmark of pheochromocytoma is its episodic nature; patients often experience paroxysms of symptoms that can be triggered by stress, changes in position, or even spontaneously.

In contrast, hyperthyroidism can cause increased heart rate and sweating, but it does not typically manifest with episodic headaches as a primary symptom. Cushing's syndrome is marked by excessive cortisol levels and might include symptoms like weight gain and hypertension, but not specifically those of episodic headache, sweating, and tachycardia as a trio. Fibromuscular dysplasia is primarily associated with vascular issues and does not typically present with the hormonal signs seen in pheochromocytoma. Thus, pheochromocytoma stands out as the condition that distinctly presents with this combination of symptoms.