NORCET 10 Mains: What is the most common cause of Cushing syndrome?

NORCET 10 Mains

Medical & Surgical Nursing

Easy

Appeared in: NORCET 10 Mains

Explanation

The most frequent cause of Cushing syndrome is the administration of exogenous glucocorticoids, often for treating inflammatory or autoimmune diseases.
This is referred to as iatrogenic (medically induced) Cushing syndrome and is far more common than any endogenous (body-produced) cause.
Medications like prednisone, when used long-term at high doses, lead to the signs and symptoms of hypercortisolism.
In this condition, the body's own production of cortisol and ACTH is suppressed due to the external supply of steroids.

Option B: A tumor of the adrenal cortex (adenoma or carcinoma) is a cause of ACTH-independent Cushing syndrome, but it is not the most common cause overall. It accounts for about 10-20% of endogenous cases.
Option C: An increase in pituitary ACTH, known as Cushing's disease, is the most common endogenous cause of Cushing syndrome. However, it is significantly less common than the exogenous (iatrogenic) cause.
Option D: Ectopic ACTH production, where a non-pituitary tumor (often in the lung) secretes ACTH, is a relatively rare cause of Cushing syndrome, accounting for about 5-10% of endogenous cases.

Clinical Relevance

Nursing practice connection: Knowing Etiology of Cushing Syndrome helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
Nurses must educate patients on long-term steroid therapy about the signs of Cushing syndrome (e.g., weight gain, moon face, easy bruising, hyperglycemia) and the importance of not stopping the medication abruptly.
Accurate patient history is crucial. A nurse's assessment can help differentiate between iatrogenic and endogenous causes by inquiring about all medications, including creams and inhalers.
What if? If a patient presents with Cushingoid features but denies any steroid use, the priority shifts to investigating endogenous causes, starting with tests to measure cortisol and ACTH levels to determine if the cause is pituitary, adrenal, or ectopic.

How to Approach the Question

First, identify the key phrase in the question: 'most common cause'. This requires you to know the relative prevalence of different etiologies.
Recognize that Cushing syndrome is a general term for excess cortisol, which can come from an external source (exogenous) or be produced by the body (endogenous).
Recall that iatrogenic (medication-induced) conditions are often more common than the spontaneous diseases they mimic. Millions of people take steroids for various medical conditions.
Compare the options: 'Exogenous steroid use' is an external cause. The other three options ('Tumor of adrenal cortex', 'Pituitary ACTH increase', 'Ectopic ACTH production') are all internal (endogenous) causes.
Conclude that the widespread use of glucocorticoid medications makes the exogenous cause the most common overall, even though pituitary tumors are the most common endogenous cause.

Concept Tested & Keywords

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