30 Questions
What is the primary function of calcium in the development of bone and teeth?
Present as calcium phosphate
What percentage of calcium in the plasma is protein-bound?
40%
What is the term for the mechanism by which the body maintains adequate calcium levels?
Calcium homeostasis
What is the percentage of ionized calcium in the plasma?
50%
What is the role of calcium in the transmission of nerve impulses?
Control of excitability
What is the term for the movement of calcium between extracellular fluid, gut, bone, and kidney?
Calcium balance
What is the primary function of parathyroid hormone (PTH) in the body?
To regulate the concentration of calcium in the ECF
What is the typical location of the parathyroid glands in the body?
Posterior to the thyroid gland
What is the molecular weight of parathyroid hormone (PTH)?
9425 Da
What is the half-life of intact PTH in the blood?
3-4 minutes
What is the region of the PTH molecule required for PTH receptor binding in target cells?
N-terminal 1-34 amino acid sequence
What is the number of amino acids in the precursor molecule of PTH?
115 amino acids
What is the pattern of plasma PTH levels throughout the day?
Highest in the early morning hours and lowest at 9 a.m.
What is the primary effect of PTH on plasma [Ca2+]?
Increase ionized calcium
Which receptor does PTH bind to in the central nervous system?
Parathyroid hormone 2 receptor
What is the net effect of PTH on glomerular filtration rate (GFR)?
Decrease GFR
What is the result of PTH's action on the distal tubule?
Increased excretion of bicarbonate
What is the time frame of PTH's delayed action on bone?
Days and weeks
What is the primary cause of hypercalcemia in primary hyperparathyroidism?
Combined effects of PTH-induced bone resorption and intestinal calcium absorption
What is the most common presenting complaint in primary hyperparathyroidism?
Renal stones
What is the underlying mechanism of secondary hyperparathyroidism?
Excessive secretion of PTH in response to hypocalcemia
What is the result of the deposition of calcium in the kidney tubules in primary hyperparathyroidism?
Impaired renal function
What is the underlying cause of hyperphosphatemia in secondary hyperparathyroidism?
Damaged renal parenchyma
What is the characteristic laboratory finding in primary hyperparathyroidism?
Hypercalcemia and hypophosphatemia
What is the effect of 1:25-DHCC on 25-HCC?
It stimulates the hydroxylation of 25-HCC
What is the effect of PTH on 1α-hydroxylase activity?
It stimulates the activity of 1α-hydroxylase
What is the role of calbindin-D in the gut?
It promotes the absorption of calcium and phosphate from the gut lumen
What is the effect of calcitriol on osteoclasts?
It stimulates the activity of osteoclasts
What is the role of alkaline phosphatase in bone formation?
It promotes the formation of new bone
What is the significance of serum osteocalcin levels?
They are a marker of bone formation and turnover
Test your knowledge on calcium metabolism, its functions, and the hormones that regulate it. Learn about vitamin D production and metabolism, and understand how calcium homeostasis works in the body.
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