This patient hypertension with hypokalemia and hyperglycemia, likely secondary to Cushing syndrome.
In Cushing syndrome, elevated cortisol levels lead to increased mineralocorticoid activity, insulin resistance, and vasoconstriction. The result is hypokalemia, hyperglycemia, and elevated blood pressure. Other signs and symptoms include weight gain, proximal muscle weakness, thinning of skin, and psychiatric disturbances (e.g. depression, psychosis, insomnia). Cushing syndrome may result from hyperplasia of the adrenal cortex, increased ACTH production from a pituitary adenoma (Cushing disease), ectopic ACTH production, or exogenous steroid administration.
Onusko reviews the causes of secondary hypertension. Up to 5 to 10 percent of hypertension cases are thought to result from secondary causes. The ABCDE mnemonic can be used to help determine a secondary cause of hypertension: Accuracy of diagnosis, obstructive sleep Apnea, Aldosteronism, presence of renal artery Bruits (suggesting renal artery stenosis), renal parenchymal disease (Bad kidneys), excess Catecholamines, Coarctation of the aorta, Cushing syndrome, Drugs, Diet, excess Erythropoietin, and Endocrine disorders. Urinalysis, CBC, electrolytes, creatinine, fasting glucose, fasting lipid levels, and a 12-lead electrocardiogram are recommended for all patients with hypertension.
Prague et al. review the laboratory evaluation of patients with suspected Cushing syndrome. If the clinical suspicion of endogenous Cushing syndrome is high, perform a confirmatory test, such as 24 hour urine collection for free cortisol (if renal function is normal) or late night salivary cortisol. If the clinical suspicion is low and the goal is to rule out Cushing, then a late night salivary cortisol or an overnight dexamethasone suppression test would be more appropriate due to their higher sensitivity. If screening tests are positive, plasma ACTH should be measured and, if suppressed, a CT scan of the adrenals should be obtained. If plasma ACTH is normal or elevated, MRI of the pituitary and sometimes CT of the chest and abdomen would follow, depending on the origin of the suspected tumor.
Illustration A depicts the various physiological manifestations of Cushing syndrome.
Answer 1: Hypothyroidism does cause weight gain and depression, but not hyperglycemia or hypokalemia.
Answer 2: Increased activity of the adrenal medulla causes weight loss, diaphoresis, anxiety, and tachycardia, in addition to hypertension due to excess catecholamine production.
Answer 3: Hyperparathyroidism may cause elevated blood pressure, but this is unlikely in a patient with a normal serum calcium level.
Answer 5: Renal artery stenosis is generally asymptomatic and would not explain this patient's weight gain, hypokalemia and hyperglycemia.
Onusko E. Diagnosing secondary hypertension. Am Fam Physician. 2003 Jan 1;67(1):67-74.
PMID: 12537168 (Link to Abstract)
Prague JK, May S, Whitelaw BC. Cushing's syndrome. BMJ. 2013 Mar 27;346:f945. doi: 10.1136/bmj.f945.
PMID: 23535464 (Link to Abstract)
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