Dehydration: This is often the most common and straightforward cause of orthostatic hypotension, resulting from insufficient fluid intake, excessive fluid loss (e.g., diarrhea, vomiting), or a combination of both. Dehydration reduces blood volume, leading to decreased cardiac output and blood pressure when standing.

Medication Side Effects: Certain medications, such as diuretics, beta-blockers, and certain antidepressants, can cause orthostatic hypotension as a side effect. These medications can either reduce blood volume or interfere with the body's ability to compensate for changes in blood pressure.
Autonomic Dysfunction: Conditions that affect the autonomic nervous system, such as diabetes, can lead to orthostatic hypotension. The autonomic nervous system plays a crucial role in regulating blood pressure, and its dysfunction can impair the body's ability to adjust blood pressure in response to changes in posture.
Blood Loss or Anemia: Significant blood loss or severe anemia can reduce the total blood volume, leading to orthostatic hypotension. Both conditions decrease the amount of blood available to maintain adequate blood pressure when standing.

Adrenal Insufficiency: Although less common, adrenal insufficiency (e.g., Addison's disease) is a critical diagnosis not to miss. It can cause orthostatic hypotension due to the lack of cortisol and aldosterone, which are essential for maintaining blood pressure.
Pheochromocytoma: This rare tumor of the adrenal gland can paradoxically cause orthostatic hypotension. While it is more commonly associated with hypertension, the intermittent release of catecholamines can lead to orthostatic hypotension due to vasodilation and volume depletion.
Neurodegenerative Diseases: Certain neurodegenerative diseases, such as Parkinson's disease and multiple system atrophy, can affect the autonomic nervous system, leading to orthostatic hypotension.

Amyloidosis: This condition involves the deposition of abnormal proteins (amyloid) in various tissues, including blood vessels and nerves, which can lead to orthostatic hypotension.
Dysautonomia: A rare condition characterized by the malfunction of the autonomic nervous system, which can cause a wide range of symptoms, including orthostatic hypotension.
Mitral Valve Prolapse: In some cases, mitral valve prolapse can lead to orthostatic hypotension, possibly due to the abnormal flow of blood through the heart or associated autonomic dysfunction.