Question

For each of the hormonal actions A–E related to the kidney, select the most appropriate option from the following list of hormones. 

1. Aldosterone. 

2. Antidiuretic hormone. 

3. Cortisol. 

4. Glucagon. 

5. Insulin.

6. Parathormone. 

7. Renin. 

8. Erythropoietin. 

A. An action that prevents glucose being lost in the urine of healthy people. 

B. An action that decreases the renal clearance of sodium and thereby increases the extracellular volume. 

C. An action that promotes the formation of angiotensin I. 

D. An action that lowers extracellular phosphate by increasing the renal clearance of phosphate. 

E. An action that tends to lower both intracellular and extracellular osmolality.

Answer 1

A. Option 5 Insulin. Insulin, by favouring rapid entry of absorbed glucose into cells for conversion to glycogen, normally keeps the blood glucose level below the renal threshold for glucose excretion. 

B. Option 1 Aldosterone. This hormone favours reabsorption of filtered sodium, thereby decreasing its clearance. The reabsorbed sodium is accompanied by chloride (following the electrical gradient) and water (following the osmotic gradient); all these are distributed mainly extracellularly, adding to the extracellular volume. 

C. Option 7 Renin. This hormone acts on the circulating precursor, angiotensinogen to form angiotensin I. 

D. Option 6 Parathormone. This hormone stimulates the release of calcium and phosphate from bone; it also increases phosphate clearance by decreasing the reabsorption of filtered phosphate from the tubules. 

E. Option 2 Antidiuretic hormone. This hormone increases reabsorption of water from the collecting ducts; as water enters the extracellular fluid its osmolality decreases; the higher intracellular osmolality draws over half this water into cells, restoring osmotic equality of the intra- and extracellular fluids.