29 Questions
What is the primary function of calcium in the body?
Structural support for bones and teeth
Which form of calcium in the plasma is considered physiologically active?
Ionized (Ca2+)
What happens if there are derangements in calcium metabolism?
Hypercalcemia or hypocalcemia
Which of the following is NOT a function of calcium in the body?
Second messenger for neurotransmitter release
What percentage of calcium in the plasma is protein-bound to albumin?
40%
Which mineral is the most abundant in the body after calcium?
Phosphorus
What is the primary function of parathyroid hormone (PTH) in the body?
To increase plasma calcium levels
Which of the following is NOT a signaling pathway activated by the binding of PTH to its receptor?
Increased protein kinase A
What is the primary effect of PTH on the kidney?
Decreases glomerular filtration rate
What is the primary mechanism by which an increase in plasma calcium concentration suppresses PTH secretion?
Increased activation of the calcium-sensing receptor on parathyroid cells
What is the difference between the rapid and delayed actions of PTH on bone?
Rapid action increases bone resorption, delayed action increases bone formation
What is the primary mechanism by which PTH increases plasma calcium levels?
Stimulating calcium release from the bones
What is the primary stimulus that leads to the release of parathyroid hormone (PTH) in secondary hyperparathyroidism?
Decreased serum calcium levels
What is the mechanism by which decreased intestinal absorption of vitamin D leads to secondary hyperparathyroidism?
Decreased mobilization of calcium from bones due to end-organ resistance to PTH
What is the major role of PTH in bone metabolism?
Increasing bone resorption
In end-stage renal failure, what is the primary mechanism leading to the development of secondary hyperparathyroidism?
Decreased synthesis of 1,25-DHCC in the remaining functioning renal tubules
How does PTH affect plasma calcium levels?
Increases plasma calcium levels
Which of the following biochemical findings would be expected in a patient with primary hyperparathyroidism?
Elevated serum calcium, normal serum phosphate, and elevated PTH
Which enzyme catalyzes the hydroxylation of cholecalciferol in the liver?
25-hydroxylase
What is the primary mechanism by which increased intracellular phosphate levels in end-stage renal failure lead to secondary hyperparathyroidism?
Increased intracellular phosphate directly inhibits the activity of the 1-hydroxylase enzyme in the remaining functioning renal tubules
Where is the 1-alpha hydroxylase enzyme located for the conversion of calcidiol to calcitriol?
Proximal convoluted tubules of nephrons
What is the result of PTH stimulating bone stem cells?
Increase in osteoclasts
What is the net result of vitamin D activation by PTH?
Increase in plasma calcium levels
How does calcitriol promote the absorption of calcium and phosphate from the gut lumen to the plasma compartment?
By acting on osteoblastic activity
Which hormone is responsible for inhibiting osteoclast activity through increased cAMP concentrations?
Calcitonin
Why does calcitonin decrease plasma calcium levels?
By increasing urine excretion of calcium and phosphate
When is plasma calcitonin elevated?
During lactation
How does calcitonin protect against calcium loss during pregnancy and lactation?
By promoting calcium mobilization from the skeleton
What is the main target cell for calcitonin's activity?
Osteoclast
Test your knowledge on calcium metabolism disorders with this quiz covering functions of calcium, hormones that regulate calcium, and vitamin D production. Learn about calcium's importance, movement in the body, and the mechanism for maintaining balance.
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