30 Questions
Which time of day is plasma PTH levels the highest?
In the early hours of the morning
What is the net effect of the activation by intact PTH at the renal tubule?
Increases GFR
Where are the high levels of the parathyroid hormone 1 receptor located?
Bone
Which signaling pathway is activated upon binding of PTH to its receptor?
Increased phospholipase C
What action does PTH have on the distal tubule in the kidney?
Activates specific receptors
What is the rapid action associated with PTH in bone?
Begins within minutes
What inhibits the activity of 1α-hydroxylase?
Hyperphosphatemia
Which enzyme catalyzes the hydroxylation of 25-HCC to 24:25-DHCC?
24-hydroxylase
What promotes the intestinal reabsorption of calcium?
Calbindin-D
Which protein is released into the bloodstream during bone formation?
Osteocalcin
What can be used as a marker of bone formation and turnover?
Serum alkaline phosphatase levels
What stimulates the mature osteoclasts leading to bone resorption?
Calcitriol
What is the most common single presenting complaint in Primary Hyperparathyroidism?
Renal stones
What is the most serious complication of Primary Hyperparathyroidism?
Deposition of calcium in kidney tubules resulting in impaired renal function
Which of the following is NOT a characteristic feature of Secondary Hyperparathyroidism?
Hypercalcemia
What causes hypercalcemia in Primary Hyperparathyroidism?
Increased intestinal calcium absorption
In Primary Hyperparathyroidism, what is responsible for the autonomous production of PTH?
Parathyroid adenoma
Which organ is most commonly affected in Primary Hyperparathyroidism?
Kidney
What is the primary target cell for calcitonin?
Osteoclast
What is the effect of calcitonin on osteoblastic activity?
It increases osteoblastic activity
During which periods is plasma [calcitonin] elevated?
During pregnancy and lactation
What is the mechanism by which calcitonin reduces plasma [Ca2+]?
By decreasing renal reabsorption of calcium and phosphate
What is the effect of calcitonin on PTH activity?
It counteracts PTH activity
How does calcitonin protect against calcium loss from the skeleton?
By protecting against calcium loss during periods of calcium mobilization
What is the effect of PTH on osteoclasts?
It stimulates their formation and activity
What is the role of 25-hydroxylase in vitamin D metabolism?
It catalyzes the formation of 25-hydroxycholecalciferol
What is the location of the 1α-hydroxylase enzyme?
In the proximal convoluted tubules of the nephrons
What is the result of PTH stimulating osteoblast activity?
An increase in plasma calcium levels
What is the role of vitamin D-binding protein?
It transports cholecalciferol to the liver
What is the effect of PTH on plasma Ca2+ and phosphate levels?
It increases plasma Ca2+ and phosphate levels
Explore the diurnal rhythm of plasma PTH levels, its response to changes in plasma calcium, and its mechanisms in increasing ionized calcium in the blood. Learn about the actions of PTH on parathyroid hormone receptors in bone and kidney.
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