How does Parathyroid Hormone (PTH / Collip's hormone) increase circulating calcium levels in human blood?
Answer and explanation
Correct answer: B. Stimulates osteoclastic bone resorption and increases renal calcium reabsorption
- Step 1: Parathyroid hormone (PTH) is a hypercalcemic hormone secreted in response to low serum .
- Step 2: It acts directly on bone to stimulate osteoclast activity, inducing demineralization and bone resorption to release and phosphate into circulation.
- Step 3: In the kidneys, PTH increases calcium reabsorption in the distal tubules and stimulates -hydroxylase to convert vitamin D into active calcitriol (), which enhances dietary calcium absorption from the intestinal lumen.
Answer
By stimulating osteoclastic bone resorption, increasing renal calcium reabsorption, and activating vitamin D for intestinal calcium absorption
Why not the others: 'By stimulating osteoblasts to deposit calcium...' describes calcitonin action, which lowers serum calcium; 'By blocking calcium absorption...' reverses PTH's effect; 'By stimulating thyroid parafollicular cells...' describes positive feedback on an antagonistic hormone, which is incorrect.
Practise more Chemical Coordination and Integration, Human Health and Disease.
Free questions with an explanation for every one, and full timed NEET UG mock tests.
More Chemical Coordination and Integration, Human Health and Disease questions
- Which peptide hormone secreted by the parafollicular cells (C-cells) of the thyroid gland acts as a hypocalcemic hormone by lowering blood c…
- Which endocrine disorder results from severe congenital hypothyroidism during pregnancy, causing stunted growth, mental retardation, and dea…
- Which lobular lymphoid and endocrine organ situated in the mediastinum near the heart secretes thymosins to promote T-lymphocyte differentia…
- Which layer of the adrenal cortex is responsible for synthesizing and secreting mineralocorticoids, primarily aldosterone?
- Why are adrenaline (epinephrine) and noradrenaline (norepinephrine) designated as 'emergency hormones' or hormones of fight-or-flight?
- Which gastrointestinal peptide hormone stimulates the exocrine pancreas to secrete water and bicarbonate ions into pancreatic juice to neutr…