NEET 2019 · BiologyPrevious Year Question
Which of the following conditions will stimulate parathyroid gland to release parathyroid hormone?
Answer: (B) Fall in blood Ca+2 levels. Answer: (b) Fall in blood Ca+2 levels Solution: Secretion of parathyroid hormone (PTH) is regulated by the circulating levels of calcium ions.
- A.Fall in active Vitamin D levels
- B.Fall in blood Ca+2 levels✓
- C.Fall in bone Ca+2 levels
- D.Rise in blood Ca+2 levels
Correct Answer
(B) Fall in blood Ca+2 levels
Solution & Explanation
Answer: (b) Fall in blood Ca+2 levels Solution: Secretion of parathyroid hormone (PTH) is regulated by the circulating levels of calcium ions. A fall in blood Ca2+ stimulates the parathyroid glands to release PTH, which then raises blood Ca2+ via bone resorption, renal reabsorption and gut absorption. Hence the direct stimulus is a fall in blood Ca2+, not bone Ca2+ or vitamin D levels. NCERT Reference: Chapter 19, Page 243, Line(s) 24-25 — "The secretion of PTH is regulated by the circulating levels of calcium ions."
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