Given below are two statements:Statement I: Calcitonin lowers blood calcium levels.Statement II: Calcitonin increases the reabsorption of calcium.Choose the correct answer:

Appeared in: BHU NO - 12 April 2024

Explanation

Statement I is correct because calcitonin's primary physiological role is to reduce blood calcium levels.
Calcitonin achieves this by inhibiting bone resorption by osteoclasts and promoting calcium deposition into the bone matrix.
Statement II is incorrect because calcitonin acts on the kidneys to decrease, not increase, the tubular reabsorption of calcium, thereby increasing its excretion in urine.
The combined effect of inhibiting calcium release from bone and increasing its excretion via the kidneys leads to a net decrease in blood calcium concentration.

Option A: This option incorrectly claims Statement I is incorrect and Statement II is correct. The physiological actions of calcitonin are the opposite: it lowers blood calcium (Statement I is correct) and decreases its reabsorption (Statement II is incorrect).
Option C: This option incorrectly claims both statements are incorrect. Statement I, 'Calcitonin lowers blood calcium levels,' is the defining function of the hormone and is factually correct.
Option D: This option incorrectly claims both statements are correct. While Statement I is correct, Statement II is incorrect. If calcitonin both lowered blood calcium and increased its reabsorption by the kidneys, these would be contradictory actions.

Clinical Relevance

Nursing practice connection: Knowing Hormonal Regulation of Calcium helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
Calcitonin (often derived from salmon, which is more potent) is used therapeutically to treat conditions of high blood calcium (hypercalcemia), Paget's disease of bone, and postmenopausal osteoporosis.
A nurse administering calcitonin would monitor the patient's serum calcium levels to assess for therapeutic effect and to prevent hypocalcemia (abnormally low calcium).
What if? If a patient had their thyroid gland surgically removed (thyroidectomy), they would lose their primary source of calcitonin. While PTH is the main regulator, the absence of calcitonin can affect the body's ability to quickly counteract a sudden surge in blood calcium.

How to Approach the Question

First, read and analyze Statement I independently. Recall the primary function of calcitonin. Is its main job to raise or lower blood calcium? This determines if Statement I is true or false.
Next, analyze Statement II independently. Consider the mechanisms by which calcitonin achieves its primary function. Does it conserve calcium in the kidneys or help excrete it? This determines if Statement II is true or false.
Once you have determined the validity of each statement (I is True, II is False), scan the options to find the one that matches your conclusion.
Be careful not to confuse the actions of calcitonin with its antagonist, parathyroid hormone (PTH), which raises blood calcium and increases its reabsorption in the kidneys.

Concept Tested & Keywords

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E6 Medicine Harrison 22e Part 2 p. 1178-1180

E6 Pharmacology KD Tripathi Essentials 9e Part 2 p. 13-15

Practise the full BHU NO - 12 April 2024

Attempt every question from this paper in a timed mock, then review the full solution for each one.