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3.2 Hormone Inactivation & Clearance โ Test 1
Q1. Compared with steroid and thyroid hormones, peptide hormones generally have:โ A shorter plasma half-life
Q2. Binding of steroid and thyroid hormones to plasma transport proteins:โ Prolongs their half-life and provides a circulating reservoir
Q3. Most thyroid and steroid hormones are inactivated and prepared for excretion mainly in the:โ Liver
Q4. Conjugation of steroid hormones (e.g. to glucuronide or sulfate) serves to:โ Increase water solubility for urinary/biliary excretion
Q5. Catecholamines are rapidly inactivated by:โ MAO and COMT
Q6. After a peptide hormone binds its surface receptor, one route of clearance is:โ Receptor-mediated endocytosis and lysosomal degradation
Q7. The kidney contributes to hormone clearance mainly by:โ Filtering and degrading small peptide hormones and excreting conjugates
Q8. Match each hormone class with its dominant inactivation route and choose the correct option.โ A-ii, B-i, C-iii
Q9. In hepatic failure, thyroxine-binding globulin (TBG) falls. The expected pattern is:โ Decreased total T4 with normal free T4 (clinically euthyroid)
Q10. The metabolic clearance rate of a hormone is the:โ Volume of plasma cleared of the hormone per unit time
Q11. Why does a continuous IV infusion of a short-half-life peptide hormone reach steady state quickly?โ Rapid clearance means equilibrium between input and removal is reached fast
Q12. Thyroid hormone is unusually long-lived in plasma mainly because it is:โ Tightly bound to TBG (and other proteins)
Q13. Cortisol is partly protected from inactivation in some tissues by 11ฮฒ-HSD; in the kidney, 11ฮฒ-HSD2:โ Converts cortisol to inactive cortisone, protecting mineralocorticoid receptors
Q14. A hormone with a very short half-life is well suited to:โ Rapid, finely-timed control (e.g. pulsatile signalling)
Q15. Urinary 17-ketosteroids are used as an index of:โ Adrenal (and gonadal) androgen production/clearance
Q16. Insulin clearance is notably affected by renal function because:โ The kidney degrades a significant fraction of circulating insulin
Q17. Free (unbound) hormone, rather than total hormone, is the fraction that:โ Is biologically active and available for clearance
Q18. A patient on long-term exogenous glucocorticoids has a suppressed axis. Abrupt withdrawal is dangerous because:โ Endogenous ACTH/cortisol cannot rise quickly, risking adrenal insufficiency
Q19. Which feature most increases a hormone's plasma half-life?โ Strong binding to a plasma transport protein
Q20. Steady-state plasma hormone concentration is determined by the balance between:โ Secretion rate and metabolic clearance rate