What is the most common cause of secondary hypertension related to Cushing's syndrome?

Excess cortisol is the most common cause of secondary hypertension related to Cushing's syndrome. Cushing's syndrome is characterized by prolonged elevated levels of cortisol, which can lead to hypertension through several mechanisms. Elevated cortisol levels can increase blood pressure by promoting sodium retention, increasing blood volume, and potentially causing vascular changes that enhance the reactivity of blood vessels. Additionally, cortisol can have indirect effects on the cardiovascular system and contribute to insulin resistance, both of which further exacerbate hypertension.

In contrast, while hyperaldosteronism can result from excess adrenal hormone production and contribute to secondary hypertension, it is not the primary mechanism in the context of Cushing's syndrome. Chronic kidney disease can also lead to hypertension due to fluid overload and activation of the renin-angiotensin-aldosterone system, but it is not directly linked to cortisol pathways. Aortic coarctation is a distinct structural abnormality that can cause secondary hypertension, but it is not related to cortisol levels or Cushing's syndrome. As such, recognizing the direct effect of excess cortisol in Cushing's syndrome is crucial in understanding its relationship with secondary hypertension.