A 45-year-old man presents with generalized weakness, easy bruisability, and truncal obesity. Laboratory tests reveal elevated midnight salivary cortisol and loss of diurnal variation. A high-dose dexamethasone suppression test suppresses cortisol by more than 50%. Which intracellular receptor mediates the genomic effects of cortisol in this patient?
- A Membrane-bound G protein-coupled receptor
- B Receptor tyrosine kinase
- C Nuclear receptor of the NR3C1 family ✓
- D Cytoplasmic guanylyl cyclase receptor
Correct answer: C. Nuclear receptor of the NR3C1 family
Explanation
Cortisol is a glucocorticoid that acts through the glucocorticoid receptor (GR), encoded by NR3B1, which is a ligand-activated transcription factor of the nuclear receptor superfamily. The receptor is cytoplasmic in the unliganded state, bound to heat shock proteins. Upon ligand binding, it translocates to the nucleus and binds glucocorticoid response elements. Membrane GPCRs, receptor tyrosine kinases, and guanylyl cyclase receptors do not mediate steroid hormone genomic effects.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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