The document discusses various endocrine causes of secondary hypertension, including pheochromocytoma, primary hyperaldosteronism, and Cushing's syndrome. Pheochromocytomas are rare tumors that produce catecholamines and can cause paroxysmal hypertension, headaches, sweating, and palpitations. Primary hyperaldosteronism is often caused by an aldosterone-producing adenoma or bilateral adrenal hyperplasia, and results in hypertension and hypokalemia. Cushing's syndrome is characterized by hypercortisolism and causes central obesity, hypertension, glucose intolerance, and other symptoms. Diagnosis of endocrine causes involves biochemical and imaging tests.