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NEET Biology: Human endocrine system-Parathyroid Practice Questions

15 free multiple-choice questions on Human endocrine system-Parathyroid (Chemical Coordination and Regulation) for NEET Biology, each with the correct answer and a step-by-step explanation. Attempt a question, then reveal the solution to check your reasoning.

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  1. Q1. Which cell type within the parathyroid gland acts as the primary sensor for extracellular calcium concentration and regulates PTH secretion in response to changes?

    • AEndothelial cells
    • BParafollicular C cells
    • CFibroblasts
    • DParathyroid chief cells
    Show answer & explanation

    Correct answer: D — Parathyroid chief cells

    The chief cells of the parathyroid gland are specialized to sense the concentration of ionized calcium in the blood and adjust the secretion of Parathyroid Hormone (PTH) accordingly.

  2. Q2. Which hormone is secreted by the thyroid gland and plays a role in activating Vitamin D synthesis?

    • AThyroid Stimulating Hormone (TSH)
    • BParathyroid Hormone
    • CGrowth Hormone
    • DCalcitonin
    Show answer & explanation

    Correct answer: A — Thyroid Stimulating Hormone (TSH)

    Thyroid Stimulating Hormone (TSH), secreted by the pituitary, stimulates the thyroid gland to produce thyroid hormones, which indirectly influence Vitamin D metabolism. (Note: While Vitamin D is synthesized in the kidney, the question focuses on the endocrine link).

  3. Q3. Which of the following is the primary target organ for the effects of Parathyroid Hormone (PTH) on calcium homeostasis?

    • AAdrenal Gland
    • BLiver
    • CPancreas
    • DKidney
    Show answer & explanation

    Correct answer: D — Kidney

    PTH primarily acts on the bones and kidneys to regulate calcium levels. The bones are the main reservoir, and the kidneys are crucial for reabsorption and excretion.

  4. Q4. If blood calcium levels are abnormally low (hypocalcemia), what is the expected response from the parathyroid glands?

    • AIncrease Calcitonin secretion
    • BDecrease PTH secretion
    • CDecrease vitamin D production
    • DIncrease PTH secretion
    Show answer & explanation

    Correct answer: D — Increase PTH secretion

    When blood calcium is low, the parathyroid glands detect this and respond by increasing the secretion of PTH to raise calcium levels.

  5. Q5. Which endocrine glands are responsible for secreting Parathyroid Hormone (PTH)?

    • AAdrenal glands
    • BPituitary gland
    • CThyroid gland
    • DParathyroid glands
    Show answer & explanation

    Correct answer: D — Parathyroid glands

    The Parathyroid glands are four small glands located behind the thyroid gland, responsible for regulating blood calcium levels by secreting PTH.

  6. Q6. What is the primary function of Calcitonin in relation to calcium homeostasis?

    • ATo regulate PTH secretion
    • BTo decrease blood calcium levels
    • CTo increase blood calcium levels
    • DTo stimulate bone breakdown
    Show answer & explanation

    Correct answer: B — To decrease blood calcium levels

    Calcitonin is secreted by the thyroid gland, and its main function is to lower elevated blood calcium levels by inhibiting osteoclast activity and promoting calcium deposition in the bone.

  7. Q7. Which hormone plays a crucial role in activating Vitamin D synthesis, which is necessary for calcium absorption from the gut?

    • AParathyroid Hormone (PTH)
    • BGrowth Hormone
    • CInsulin
    • DCalcitonin
    Show answer & explanation

    Correct answer: A — Parathyroid Hormone (PTH)

    PTH stimulates the kidneys to convert inactive Vitamin D into its active form (calcitriol), which is essential for intestinal absorption of calcium.

  8. Q8. The primary role of Parathyroid Hormone (PTH) in the maintenance of calcium homeostasis is to act upon which endocrine glands to achieve this balance?

    • APituitary gland
    • BThyroid gland
    • CAdrenal glands
    • DParathyroid glands
    Show answer & explanation

    Correct answer: D — Parathyroid glands

    PTH acts primarily on the bone (to release calcium), the kidneys (to increase calcium reabsorption and activate Vitamin D), and indirectly on the intestines (via Vitamin D) to regulate blood calcium levels.

  9. Q9. The main effect of Parathyroid Hormone (PTH) on the kidneys regarding calcium is to promote:

    • AIncreased secretion of Vitamin D
    • BIncreased reabsorption of calcium
    • CIncreased excretion of phosphate
    • DIncreased excretion of calcium
    Show answer & explanation

    Correct answer: D — Increased excretion of calcium

    PTH stimulates the kidneys to increase the reabsorption of calcium from the filtrate back into the blood, which helps raise systemic calcium levels.

  10. Q10. Which of the following is the primary action of Parathyroid Hormone (PTH) on the bones in the context of calcium homeostasis?

    • ATo stimulate osteoblasts to form new bone tissue
    • BTo increase the deposition of calcium into the bone matrix
    • CTo promote the resorption (breakdown) of bone tissue
    • DTo inhibit the activity of osteoclasts
    Show answer & explanation

    Correct answer: C — To promote the resorption (breakdown) of bone tissue

    Parathyroid hormone (PTH) acts on bone tissue by stimulating osteoclasts, which are responsible for breaking down bone matrix and releasing calcium and phosphate into the blood, thereby raising blood calcium levels.

  11. Q11. Which hormone is primarily responsible for increasing blood calcium levels by stimulating osteoclasts to resorb bone tissue?

    • AGrowth Hormone
    • BCalcitonin
    • CParathyroid Hormone (PTH)
    • DVitamin D
    Show answer & explanation

    Correct answer: C — Parathyroid Hormone (PTH)

    Parathyroid Hormone (PTH) stimulates osteoclasts, which breaks down bone matrix, releasing calcium ions into the bloodstream, thereby increasing blood calcium levels.

  12. Q12. Which hormone is produced by the parathyroid glands in response to low blood calcium concentration?

    • AParathyroid Hormone (PTH)
    • BGrowth Hormone
    • CCalcitonin
    • DInsulin
    Show answer & explanation

    Correct answer: A — Parathyroid Hormone (PTH)

    When blood calcium levels fall, the parathyroid glands detect this and respond by releasing increased amounts of PTH.

  13. Q13. Parathyroid glands are located in which region of the neck?

    • AThyroid gland
    • BLarynx
    • CPituitary gland
    • DThymus gland
    Show answer & explanation

    Correct answer: B — Larynx

    The parathyroid glands are typically situated on the posterior surface of the thyroid gland.

  14. Q14. The main function of Parathyroid Hormone (PTH) in relation to blood calcium levels is to:

    • AIncrease the absorption of Vitamin D
    • BIncrease serum calcium levels
    • CDecrease the secretion of Calcitonin
    • DReduce the reabsorption of calcium in the renal tubules
    Show answer & explanation

    Correct answer: B — Increase serum calcium levels

    PTH acts to raise blood calcium levels by stimulating bone resorption and increasing renal calcium reabsorption.

  15. Q15. If blood calcium levels fall below the normal range, what is the immediate response mediated by the parathyroid glands?

    • ARelease of Parathyroid Hormone (PTH)
    • BSecretion of Calcitonin
    • CIncreased secretion of Growth Hormone
    • DInhibition of Vitamin D synthesis
    Show answer & explanation

    Correct answer: A — Release of Parathyroid Hormone (PTH)

    When calcium levels drop, the parathyroid glands sense this and rapidly release Parathyroid Hormone (PTH) to raise blood calcium.

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