A patient with hypertension, palpitations, and excessive sweating is most likely suffering from:

The symptoms presented—hypertension, palpitations, and excessive sweating—are characteristic manifestations of pheochromocytoma. This is a rare tumor of the adrenal glands that leads to excessive production of catecholamines, such as epinephrine and norepinephrine. These hormones are responsible for the body's "fight or flight" response, which induces symptoms like increased heart rate (palpitations), high blood pressure (hypertension), and sweating due to the activation of the sympathetic nervous system.

In contrast, hypoparathyroidism is associated with low calcium levels leading to muscle cramps and seizures, not hypertension or excessive sweating. Cushing syndrome results from excess cortisol and typically presents with features like weight gain, moon facies, and skin changes, rather than the specific triad of symptoms observed here. Hyperpituitarism involves an overproduction of pituitary hormones which can lead to various systemic effects but does not typically manifest with the acute sympathetic symptoms evidenced by this patient.

Given this context, the symptoms align closely with pheochromocytoma, making it the most likely diagnosis.