Essential Hypertension: This is the most common cause of high blood pressure, accounting for about 90-95% of cases. It is a diagnosis of exclusion, meaning that other causes of hypertension must be ruled out before making this diagnosis. Essential hypertension is often associated with a family history, obesity, and lifestyle factors.

Chronic Kidney Disease (CKD): CKD is a common cause of secondary hypertension. High blood pressure can both cause and be a consequence of kidney disease, creating a vicious cycle.
Sleep Apnea: This condition is increasingly recognized as a cause of secondary hypertension. The intermittent hypoxia and frequent awakenings associated with sleep apnea can lead to increased sympathetic tone and blood pressure.
Primary Aldosteronism: This condition, characterized by excessive production of aldosterone, is a common cause of secondary hypertension. It can lead to resistant hypertension and is often associated with hypokalemia.
Thyroid Disease: Both hyperthyroidism and hypothyroidism can cause changes in blood pressure. Hyperthyroidism is more commonly associated with hypertension.

Pheochromocytoma: A rare tumor of the adrenal gland that produces excess catecholamines, leading to episodic or sustained hypertension. Missing this diagnosis can be fatal due to the risk of hypertensive crises.
Aortic Coarctation: A congenital narrowing of the aortic isthmus, which can cause severe hypertension in the arms, with decreased or delayed pulses in the lower extremities. Untreated, it can lead to heart failure, aortic dissection, or cerebral hemorrhage.
Renal Artery Stenosis: Narrowing of the renal arteries can cause renovascular hypertension. It is a critical diagnosis to consider, especially in patients with resistant hypertension or those with atherosclerotic disease.

Cushing's Syndrome: A rare endocrine disorder caused by excess cortisol production, which can lead to hypertension among other symptoms.
Hyperparathyroidism: Elevated parathyroid hormone levels can cause hypertension, though this is less common.
Pregnancy-Induced Hypertension: Includes conditions like preeclampsia and eclampsia, which are unique to pregnancy and can be life-threatening if not promptly diagnosed and managed.
Medication-Induced Hypertension: Certain medications, such as NSAIDs, steroids, and some antidepressants, can cause or exacerbate hypertension.