A depressed patient receives 1 mg of dexamethasone at night; plasma cortisol the following afternoon remains elevated instead of falling. Failure to suppress in the dexamethasone suppression test indicates:

• A Impaired negative feedback of the hypothalamo-pituitary-adrenal axis with cortisol hypersecretion ✓
• B Primary adrenal cortical insufficiency
• C Reduced corticotropin-releasing hormone drive from the hypothalamus
• D Enhanced sensitivity of central glucocorticoid receptors

Explanation

In melancholic depression the hypothalamo-pituitary-adrenal axis is hyperactive, with raised CRH and cortisol and reduced suppressibility by exogenous steroid, indicating impaired glucocorticoid receptor mediated feedback. Non-suppression supports the diagnosis of endogenous or psychotic depression and correlates with risk of relapse. Primary adrenal insufficiency causes low rather than high cortisol, and enhanced receptor sensitivity would produce greater, not lesser, suppression of the axis.

Reference: Kaplan and Sadock's Synopsis of Psychiatry, 12th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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