Which steroid hormone–receptor complex exerts its primary genomic effect by binding to hormone response elements (HREs) as a homodimer and regulating gene transcription in the nucleus?

• A Glucocorticoid (cortisol) — glucocorticoid receptor homodimer on GREs ✓
• B Thyroid hormone (T3) — nuclear receptor homodimer on TREs
• C Aldosterone — mineralocorticoid receptor monomer on MREs
• D Vitamin D3 (calcitriol) — VDR:RXR heterodimer on VDREs

Explanation

Glucocorticoids (e.g., cortisol) bind cytoplasmic glucocorticoid receptors (GRs), causing dissociation of Hsp90 chaperones and translocation of the ligand-GR complex into the nucleus. The ligand-bound GR functions as a homodimer binding glucocorticoid response elements (GREs) and either activates or represses gene transcription. Thyroid hormone receptor (TR) and vitamin D receptor (VDR) function as heterodimers with RXR on their respective response elements; aldosterone–mineralocorticoid receptor can also bind as a homodimer, but VDR:RXR heterodimer is the canonical answer for vitamin D genomic action.

Reference: Harper's Illustrated Biochemistry, 32nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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