zaki
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A 54-year-old man with a 5-year history of hypertension, facial fullness, and truncal obesity presents with several days of midthoracic back pain. The pain started suddenly after he tripped on the stairs, missed a step, and landed on his buttocks.
Physical examination shows a cushingoid-appearing man with a blood pressure of 160/100 mm Hg. His serum potassium level is 3 meq/L, and his fasting plasma glucose concentration is 142 mg/dL. A 24-hour urine collection sample shows a cortisol excretion rate of 424 µg/dL. A radiograph of his thoracic spine shows a compression fracture at T8.
What would you do now?
(A) Order a low-dose (1 mg) overnight dexamethasone suppression test.
(B) Order computed tomography (CT) of the abdomen.
(C) Order magnetic resonance imaging of the sella with gadolinium.
(D) Order morning measurement of adrenocorticotropic hormone (ACTH) levels.
(E) Order an inferior petrosal sinus catheterization and sampling for ACTH before and after corticotropin-releasing hormone administration.
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Maverick
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| veri
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The answer is A?
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| alice8
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(A) Order a low-dose (1 mg) overnight dexamethasone suppression test. :?:
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| gballarino
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I´ll go for (A). Low dose overnight suppresion test.
Altough, I think that in this particular case, given that the clinical picture is so straightforward, we can skip the screening test (overnight) and go directly to the diagnostic test... the full 2-day, low dose, dexamethasone suppresion test. Pitty that´s not an option.
All ther other options are for finding the etiology of the elevated cortisol level, and should be performed as indicated, after the diagnosis of Cushing Syndrome has been confirmed.
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| gballarino
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I´ve been thinking... (D) it´s not actually so unlikely to be correct. 24 hour-urine cortisol level, though too variable (hence uncertain), it´s really elevated. Perhaps we can consider it enough evidence of cortisol excess (cushing syndrome).
If this is true, ACTH measurement would be a sensible next step to determine if cortisol is being produced autonomously from the adrenals, or as a consequence of elevated ACTH.
However, he is under stress... (hospitalized, traumatized, with a spine fracture), and that alone would rise his blood and urine cortisol levels. So, a suppresion test is necesary after all. Well... I think i´ll stick to (A).
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| zaki
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Answer: D
Educational Objective: Determine the cause of Cushing’s syndrome.
This patient has clear clinical (hypertension, truncal obesity, osteoporotic vertebral fracture) and biochemical (hypokalemia, hyperglycemia, and elevated cortisol excretion) evidence of Cushing’s syndrome. The diagnostic challenge is to determine the cause of the excess cortisol production. The next step, therefore, is to assess the adrenocorticotropic hormone (ACTH) level. If it is normal or elevated, a pituitary or ectopic source needs to be sought; if the ACTH level is low, an adrenal cause is indicated.
Because the diagnosis of Cushing’s syndrome is already clear, an overnight dexamethasone suppression test would not forward the diagnostic process.
The relatively high incidence of incidental pituitary and adrenal adenomas makes imaging with either computed tomography or magnetic resonance imaging a poor choice in the evaluation of this patient.
Petrosal sinus sampling may be helpful in separating ectopic ACTH production from pituitary-based Cushing’s syndrome (Cushing’s disease) and should be considered in this case if the ACTH level is not suppressed. The test requires placing catheters in the petrosal sinuses and involves bilateral sampling for ACTH. Higher levels of ACTH on one side compared with the other and compared with the periphery provide not only evidence for a pituitary source but also localizing information. Administration of corticotropin-releasing hormone (CRH) may enhance the yield of petrosal sinus sampling or may be used without petrosal sampling to assess pituitary responsiveness. Low or absent response of ACTH and cortisol to CRH is seen in ectopic ACTH production and autonomous adrenal hyperfunction; an exaggerated response is seen in pituitary-based Cushing’s disease.
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| gballarino
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I´ve been reading... neither 24 hr urine cortisol nor suppresion tests are specific enough in acutely ill patients. Anyways, they are all there is to it; furthermore, 24 hr urine cortisol seems to be a better screening method than overnight dexa suppresion test, and is recomended when case is not clear cut, such as in obese patients.
So... ok... We DO know that the patient has Cushing Syndrome. I was wrong.
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| Moozy
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but dont you think we need to document cushings syndrome first by doing a Dexamethasone suppression test and then find out the cause for the disease by checking for ACTH levels no matter how sure we are.
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| Moozy
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Okay.,.. i agree with the answer now...
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