Mechanism of hormone action MCQs With Answer

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Mechanism of hormone action MCQs With Answer is an essential resource for B. Pharm students preparing for pharmacology and endocrine modules. This concise, Student-friendly post covers receptor types, signal transduction pathways, second messengers (cAMP, IP3/DAG, cGMP), nuclear receptor genomics, receptor regulation, and pharmacological modulation of hormone action. Focused keywords such as mechanism of hormone action, hormone receptors, signal transduction, second messengers, endocrine pharmacology, and MCQs help improve search visibility and study relevance. Each MCQ probes core concepts and clinical correlations to deepen understanding and exam readiness. Now let’s test your knowledge with 50 MCQs on this topic.

Q1. Which receptor type is primarily associated with steroid hormone action?

  • Cytoplasmic/nuclear receptor
  • G protein–coupled receptor (GPCR)
  • Receptor tyrosine kinase (RTK)
  • Ligand-gated ion channel

Correct Answer: Cytoplasmic/nuclear receptor

Q2. Activation of Gs protein typically leads to increase in which second messenger?

  • cAMP
  • IP3
  • cGMP
  • Calcium

Correct Answer: cAMP

Q3. Which G protein subtype activates phospholipase C to generate IP3 and DAG?

  • Gq
  • Gi
  • Gs
  • G12/13

Correct Answer: Gq

Q4. Nitric oxide (NO) mediates vasodilation via activation of which enzyme?

  • Soluble guanylate cyclase
  • Adenylate cyclase
  • Phospholipase C
  • Protein kinase A

Correct Answer: Soluble guanylate cyclase

Q5. Which enzyme is primarily responsible for termination of cAMP signaling?

  • Phosphodiesterase
  • Adenylate cyclase
  • Protein kinase A
  • Phospholipase C

Correct Answer: Phosphodiesterase

Q6. The DNA-binding domain of nuclear hormone receptors is characterized by which structural motif?

  • Zinc finger motif
  • Leucine zipper
  • SH2 domain
  • EF-hand motif

Correct Answer: Zinc finger motif

Q7. Insulin exerts its effects mainly through which receptor mechanism?

  • Receptor tyrosine kinase activation leading to autophosphorylation
  • Nuclear receptor-mediated gene transcription
  • Ligand-gated ion channel opening
  • Direct activation of adenylate cyclase

Correct Answer: Receptor tyrosine kinase activation leading to autophosphorylation

Q8. Thyroid hormones primarily regulate target cells by which mechanism?

  • Binding to nuclear receptors and modulating gene transcription
  • Activating adenylate cyclase via GPCRs
  • Opening ligand-gated ion channels
  • Direct enzymatic modulation in cytosol

Correct Answer: Binding to nuclear receptors and modulating gene transcription

Q9. Hormone response elements (HREs) are located where relative to regulated genes?

  • In promoter regions of target genes
  • Within mitochondrial DNA
  • In the introns of unrelated genes only
  • On the cell membrane

Correct Answer: In promoter regions of target genes

Q10. Which second messenger directly causes release of intracellular Ca2+ from the endoplasmic reticulum?

  • Inositol 1,4,5-trisphosphate (IP3)
  • Cyclic AMP (cAMP)
  • cGMP
  • DAG (diacylglycerol)

Correct Answer: Inositol 1,4,5-trisphosphate (IP3)

Q11. Diacylglycerol (DAG) primarily activates which protein kinase?

  • Protein kinase C (PKC)
  • Protein kinase A (PKA)
  • Tyrosine kinase
  • AMP-activated protein kinase (AMPK)

Correct Answer: Protein kinase C (PKC)

Q12. Which of the following is a classic example of a receptor with intrinsic tyrosine kinase activity?

  • Insulin receptor
  • B2-adrenergic receptor
  • Nicotinic acetylcholine receptor
  • Glucocorticoid receptor

Correct Answer: Insulin receptor

Q13. The JAK/STAT signaling pathway is most characteristically associated with which receptor family?

  • Cytokine receptors (e.g., interferons, growth hormone)
  • GPCRs
  • Receptor tyrosine kinases
  • Nuclear steroid receptors

Correct Answer: Cytokine receptors (e.g., interferons, growth hormone)

Q14. Which example best represents a non-genomic action of a steroid hormone?

  • Rapid endothelial nitric oxide production induced by estrogen
  • Altered transcription of hepatic enzymes after cortisol exposure
  • Induction of protein synthesis by thyroid hormone over hours
  • Binding of steroid to intracellular receptor and DNA

Correct Answer: Rapid endothelial nitric oxide production induced by estrogen

Q15. Which plasma binding protein is the primary carrier of thyroxine (T4)?

  • Thyroxine-binding globulin (TBG)
  • Albumin
  • Sex hormone–binding globulin (SHBG)
  • Transferrin

Correct Answer: Thyroxine-binding globulin (TBG)

Q16. Atrial natriuretic peptide (ANP) exerts effects via which receptor mechanism?

  • Membrane-bound guanylate cyclase increasing cGMP
  • GPCR increasing cAMP
  • Nuclear receptor-mediated transcription
  • Ligand-gated ion channel opening

Correct Answer: Membrane-bound guanylate cyclase increasing cGMP

Q17. Which hormone has a relatively long plasma half-life compared to others?

  • Thyroxine (T4)
  • Insulin
  • Epinephrine
  • Atrial natriuretic peptide

Correct Answer: Thyroxine (T4)

Q18. A permissive effect in endocrinology refers to which concept?

  • One hormone enhances the action of another hormone without producing the effect itself
  • Two hormones produce identical effects independently
  • Hormone synthesis is inhibited by another hormone
  • Hormone effects are confined to permissive tissues only

Correct Answer: One hormone enhances the action of another hormone without producing the effect itself

Q19. Signal amplification in hormone action most often occurs at which step?

  • Activation of many intracellular effector enzymes by a single receptor–G protein complex
  • Binding of one hormone to a single receptor with no further events
  • Transcriptional repression by nuclear receptors
  • Receptor internalization

Correct Answer: Activation of many intracellular effector enzymes by a single receptor–G protein complex

Q20. GPCR desensitization commonly involves which mechanism?

  • Phosphorylation by G protein–coupled receptor kinases (GRKs) followed by β-arrestin binding
  • Direct DNA methylation of receptor gene
  • Increased ligand synthesis
  • Immediate receptor tyrosine phosphorylation

Correct Answer: Phosphorylation by G protein–coupled receptor kinases (GRKs) followed by β-arrestin binding

Q21. Chronic exposure to high concentrations of an agonist often results in which receptor adaptation?

  • Downregulation via endocytosis and degradation
  • Immediate increase in receptor gene transcription
  • Permanently increased receptor sensitivity
  • Irreversible covalent activation of receptor

Correct Answer: Downregulation via endocytosis and degradation

Q22. Which domain of nuclear hormone receptors is responsible for ligand binding?

  • Ligand-binding domain (LBD)
  • DNA-binding domain (DBD)
  • Transmembrane domain
  • SH3 domain

Correct Answer: Ligand-binding domain (LBD)

Q23. The metabolic actions of insulin that lead to GLUT4 translocation are mediated mainly through which pathway?

  • PI3K–Akt pathway
  • cAMP–PKA pathway
  • JAK–STAT pathway
  • cGMP–PKG pathway

Correct Answer: PI3K–Akt pathway

Q24. Glucagon increases hepatic glucose output primarily by activating which enzyme system?

  • Adenylate cyclase → increased cAMP → PKA activation
  • Phospholipase C → increased IP3 and DAG
  • Guanylate cyclase → increased cGMP
  • Tyrosine kinase cascade

Correct Answer: Adenylate cyclase → increased cAMP → PKA activation

Q25. Which statement correctly contrasts Gs and Gi protein function?

  • Gs stimulates adenylate cyclase; Gi inhibits adenylate cyclase
  • Gs opens ion channels; Gi closes ion channels only
  • Gs activates PLC; Gi activates guanylate cyclase
  • Gs and Gi have identical effects on cAMP

Correct Answer: Gs stimulates adenylate cyclase; Gi inhibits adenylate cyclase

Q26. Epidermal growth factor receptor (EGFR) is an example of which receptor type?

  • Receptor tyrosine kinase (RTK)
  • GPCR
  • Ligand-gated ion channel
  • Nuclear receptor

Correct Answer: Receptor tyrosine kinase (RTK)

Q27. cAMP-dependent protein kinase is also known as which enzyme?

  • Protein kinase A (PKA)
  • Protein kinase C (PKC)
  • Protein kinase G (PKG)
  • Tyrosine kinase

Correct Answer: Protein kinase A (PKA)

Q28. Which enzyme hydrolyzes phosphatidylinositol 4,5-bisphosphate (PIP2) to IP3 and DAG?

  • Phospholipase C (PLC)
  • Phospholipase A2 (PLA2)
  • Phospholipase D (PLD)
  • Phospholipase B (PLB)

Correct Answer: Phospholipase C (PLC)

Q29. Sildenafil enhances penile erection by inhibiting PDE5, which increases levels of which second messenger?

  • cGMP
  • cAMP
  • IP3
  • Calcium

Correct Answer: cGMP

Q30. Lipophilicity of steroid hormones primarily enables which property relevant to mechanism of action?

  • Diffusion across the cell membrane to reach intracellular receptors
  • Exclusive action at cell-surface receptors
  • Rapid enzymatic degradation in plasma
  • Inability to bind plasma carrier proteins

Correct Answer: Diffusion across the cell membrane to reach intracellular receptors

Q31. In receptor–ligand kinetics, a lower dissociation constant (KD) indicates what about affinity?

  • Higher affinity of ligand for receptor
  • Lower affinity of ligand for receptor
  • No change in affinity
  • Irreversible binding

Correct Answer: Higher affinity of ligand for receptor

Q32. A competitive antagonist at a receptor typically produces which effect on a dose–response curve?

  • Rightward shift (increased EC50) without change in Emax
  • Decrease in Emax without shift in EC50
  • Leftward shift with increased Emax
  • Complete loss of receptor expression

Correct Answer: Rightward shift (increased EC50) without change in Emax

Q33. Elevated cortisol levels cause negative feedback primarily at which anatomical sites?

  • Hypothalamus and anterior pituitary
  • Adrenal medulla
  • Thyroid gland
  • Pancreatic islets

Correct Answer: Hypothalamus and anterior pituitary

Q34. Which receptor type mediates the most rapid changes in membrane potential in response to ligand binding?

  • Ligand-gated ion channels
  • Nuclear receptors
  • Receptor tyrosine kinases
  • GPCRs acting via transcription

Correct Answer: Ligand-gated ion channels

Q35. Between T3 and T4, which has higher affinity for thyroid hormone receptors and greater biological potency?

  • T3 (triiodothyronine)
  • T4 (thyroxine)
  • Both have equal affinity
  • Neither binds nuclear receptors

Correct Answer: T3 (triiodothyronine)

Q36. Which drug increases cGMP levels by inhibiting PDE5 and is used to treat erectile dysfunction?

  • Sildenafil
  • Propranolol
  • Metformin
  • Prednisone

Correct Answer: Sildenafil

Q37. Glucocorticoids exert anti-inflammatory effects partly by inducing which inhibitory protein?

  • Lipocortin (annexin A1) which inhibits phospholipase A2
  • Cyclooxygenase-2 (COX-2) induction
  • NF-κB activation
  • Increased synthesis of prostaglandins

Correct Answer: Lipocortin (annexin A1) which inhibits phospholipase A2

Q38. Receptor dimerization and autophosphorylation are key activation events in which receptor class?

  • Receptor tyrosine kinases (RTKs)
  • GPCRs
  • Ligand-gated ion channels
  • Nuclear receptors

Correct Answer: Receptor tyrosine kinases (RTKs)

Q39. Plasma binding proteins for hormones primarily affect which parameter of hormone pharmacokinetics?

  • Distribution and free (bioavailable) fraction
  • Immediate receptor activation
  • Conversion to active metabolites inside cells
  • Direct agonism of cell-surface receptors

Correct Answer: Distribution and free (bioavailable) fraction

Q40. For intracellular receptor-mediated genomic actions, what must occur after ligand binding?

  • Translocation of the receptor–ligand complex to the nucleus and DNA binding
  • Immediate opening of ion channels on the plasma membrane
  • Direct activation of G proteins at the membrane
  • Ubiquitin-dependent proteasomal degradation

Correct Answer: Translocation of the receptor–ligand complex to the nucleus and DNA binding

Q41. Heterotrimeric G proteins are composed of which subunits?

  • Alpha, beta, and gamma subunits
  • Alpha and delta subunits only
  • Beta and gamma only
  • Single polypeptide chain without subunits

Correct Answer: Alpha, beta, and gamma subunits

Q42. Which environmental chemical is a known xenoestrogen that can bind estrogen receptors?

  • Bisphenol A (BPA)
  • Paracetamol
  • Insulin
  • Vitamin D

Correct Answer: Bisphenol A (BPA)

Q43. Prolonged agonist exposure of β-adrenergic receptors leads to decreased responsiveness primarily via which process?

  • Phosphorylation by GRKs and β-arrestin–mediated internalization
  • Permanently increased receptor gene expression
  • Complete conversion to nuclear receptors
  • Immediate receptor oligomerization into active form

Correct Answer: Phosphorylation by GRKs and β-arrestin–mediated internalization

Q44. Vasopressin V2 receptors in the kidney increase water reabsorption via which second messenger?

  • cAMP
  • IP3
  • cGMP
  • Direct calcium influx through channels

Correct Answer: cAMP

Q45. Thyroid hormone receptors commonly form heterodimers with which partner to bind DNA?

  • Retinoid X receptor (RXR)
  • Glucocorticoid receptor (GR)
  • Estrogen receptor (ER)
  • Beta-adrenergic receptor

Correct Answer: Retinoid X receptor (RXR)

Q46. Which subunit of the insulin receptor possesses intrinsic tyrosine kinase activity?

  • Beta (β) subunit
  • Alpha (α) subunit
  • Gamma (γ) subunit
  • Delta (δ) subunit

Correct Answer: Beta (β) subunit

Q47. Nuclear receptor coactivators typically enhance transcription by which mechanism?

  • Histone acetylation to relax chromatin structure
  • DNA methylation to silence genes
  • Cleavage of receptor proteins
  • Blocking RNA polymerase binding

Correct Answer: Histone acetylation to relax chromatin structure

Q48. Peptide hormones are initially synthesized as which precursors in the rough endoplasmic reticulum?

  • Preprohormones
  • Steroid precursors
  • Free amino acids only
  • Functional mature hormones directly

Correct Answer: Preprohormones

Q49. Chronic exposure to receptor antagonists commonly leads to which adaptive change in receptor number?

  • Upregulation (increased receptor expression)
  • Downregulation (decreased receptor expression)
  • Immediate receptor gene deletion
  • Conversion of receptor class to ion channel

Correct Answer: Upregulation (increased receptor expression)

Q50. A key molecular mechanism contributing to insulin resistance involves modification of insulin signaling through which process?

  • Serine phosphorylation of insulin receptor substrate (IRS) proteins impairing downstream signaling
  • Increased tyrosine phosphorylation of IRS enhancing signaling
  • Complete loss of insulin gene in pancreas
  • Excessive activation of soluble guanylate cyclase

Correct Answer: Serine phosphorylation of insulin receptor substrate (IRS) proteins impairing downstream signaling

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