Calcium-Phosphate homeostasis Flashcards
During aging, what happens to the amount of calcium absorbed from dietary intake?
Decreases
Hyperreflexia, spontaneous twitching, muscle cramps, and tingling/numbness are symptoms of?
Hypocalcemia
What is an indicator of hypocalcemia that deals with twitching of the facial muscles elicited by tapping on the facial nerve?
Chvostek sign
What is an indicator of hypocalcemia that deals with carpopedal spasm upon inflation of a blood pressure cuff?
Trousseau sign
Decreased QT interval, constipation, lack of appetite, polyuria, polydipsia, muscle weakness, hyporeflexia, lethargy, and coma are symptoms of?
Hypercalcemia
An increase in membrane excitability and generation of spontaneous AP are seen in hypocalcemia or hypercalcemia?
Hypocalcemia
If you increase plasma protein concentration, what happens to the total calcium concentration?
Increases
If you increased phosphate concentration, what happens to the ionized calcium concentration?
Decreases
When free ionized calcium concentration increases because less calcium is bound to albumin describes what term?
Acidemia
When free ionized calcium concentration decreases because more calcium is bound to albumin describes what term?
Alkalemia
What is alkalemia most often accompanied by?
Hypocalcemia
To maintain calcium balance, kidneys must excrete the same amount of calcium that is absorbed by?
GI tract
What cells of the parathyroid gland synthesize and secrete PTH?
Chief cells
When is PTH stimulation for secretion?
When there’s a decrease in calcium concentration in plasma
What inhibits PTH synthesis and secretion?
Increased extracellular calcium
What causes decrease synthesis and storage of PTH, increase breakdown of stored PTH and release of inactive PTH fragment into circulation?
Chronic hypercalcemia
What causes increase synthesis and storage of PTH and hyperplasia of parathyroid glands (secondary hyperparathyroidism)?
Chronic hypocalcemia
What is the result of chronic magnesium depletion and inhibits PTH synthesis, storage, and secretion?
Severe hypomagnesemia
What is the most often cause of severe hypomagnesemia?
Alcoholism
What is the PTH action on bone?
Resorption
Phosphate reabsorption, calcium reabsorption, and urinary cAMP are the results of PTH action on what structure?
Kidney
Increased calcium absorption indirectly via vitamin D (1, 25-dihydroxycholecalciferol) are the results of PTH action on what structure?
Intestine
Vitamin D increases the concentration of what in the plasma?
Calcium and phosphate
Cholecalciferol is equivalent to?
Vitamin D
CYP1-alpha gene produces what kidney enzyme?
1alpha-hydroxylase
Where are PTH receptors located on?
Osteoblasts
Vitamin D and PTH act synergistically to stimulate?
Osteoclast activity and bone resorption
What induces stem cells to differentiate into osteoclast precursors, mononuclear osteoclasts, and finally mature multinucleated osteoclasts?
M-CSF (macrophage colony-stimulating factor)
What is a cell surface protein that is the primary mediator of osteoclast formation?
RANKL
What is the cell surface protein receptors on osteoclasts and osteoblasts precursors?
RANK
What is a soluble protein produced by osteoblasts and inhibits RANKL/RANK interaction?
OPG (osteoprotegerin)
What increases RANKL?
What decreases OPG?
1) PTH and vitamin D
2) PTH
Inhibition of the sodium/phosphate transporter (NPT) by PTH causes?
Phosphaturia (increased excretion of phosphate in urine)
The cAMP generated in what cells caused it to be excreted in the urine?
Cells of the proximal tubule
What stimulates 1alpha-hydroxylase activity?
PTH
PTH stimulates calcium reabsorption in what area of the kidney?
Ascending limb of Henle’s loop and distal tubule
What effect does vitamin D have in the small intestine?
Increases calcium and phosphate absorption
What effect does vitamin D have in the kidney?
Promotes phosphate reabsorption (stimulates NPT2a expression)
What effect does vitamin D have in the parathyroid gland?
1) Inhibits PTH gene expression
2) Stimulates CaSR gene expression
What decreases blood calcium and phosphate concentration by inhibiting bone resorption?
Calcitonin
Calcitonin receptors are expressed on?
Osteoclasts
What does calcitonin do to osteoclasts?
Decreases activity and number
What is the major stimulus of calcitonin?
Increased plasma calcium
What causes a decrease in calcitonin but no effect in calcium metabolism?
Thyroidectomy
What causes an increase in calcitonin but no effect in calcium metabolism?
Thyroid tumors
What stimulates intestinal calcium absorption and renal tubular calcium reabsorption and is one of the most potent regulators of osteoblast and osteoclast function?
Estradiol-17beta
What promotes survival of osteoblasts and apoptosis of osteoclasts; favoring bone formation over resorption?
Estrogen
What promotes bone resorption and renal calcium wasting and inhibits intestinal calcium absorption?
Cortisol
Patients treated with high levels of a glucocorticoid can develop?
Glucocorticoid induced osteoporosis
What do patients with primary hyperparathyroidism present with?
1) Hypercalciuria (stones)
2) Increased bone resorption
3) Constipation
(Stones, bones, and groans)
Patients with primary hyperparathyroidism excrete excessive amounts of?
Phosphate, cAMP, and calcium
What is the treatment for primary hyperparathyroidism?
Parathyroidectomy
What are the levels of 1) PTH, 2) Ca2+, 3) Phosphate, 4) Vitamin D in patients with primary hyperparathyroidism?
1) Increased
2) Increased
3) Decreased
4) Increased
What levels are low in the blood with secondary hyperparathyroidism?
Calcium
What are the levels of 1) PTH, 2) Ca2+, 3) Phosphate, 4) Vitamin D in patients with secondary hyperparathyroidism caused by renal failure?
1) Increased
2) Decreased
3) Increased
4) Decreased
What are the levels of 1) PTH, 2) Ca2+, 3) Phosphate, 4) Vitamin D in patients with secondary hyperparathyroidism caused by Vitamin D deficiency?
1) Increased
2) Decreased
3) Decreased
4) Decreased
Thyroid and parathyroid surgery are some causes of?
Hypoparathyroidism
What is the treatment for hypoparathyroidism?
Oral calcium supplement
What are the levels of 1) PTH, 2) Ca2+, 3) Phosphate, 4) Vitamin D in patients with hypoparathyroidism?
1) Decreased
2) Decreased
3) Increased
4) Decreased
What disorder is inherited in autosomal dominant fashion and results in the G(s) for PTH in bone and kidney being defective?
Patients present with short stature, short neck, obesity, subcutaneous calcification, shortened metatarsals and metacarpals
Albright hereditary osteodystrophy
Pseudohypoparathyroidism type 1a
What condition develop in Albright hereditary osteodystrophy?
Hypocalcemia and hyperphosphatemia
What are the levels of 1) PTH, 2) Ca2+, 3) Phosphate, 4) Vitamin D in patients with Albright hereditary osteodystrophy?
1) Increased
2) Decreased
3) Increased
4) Decreased
Humoral hypercalcemia of malignancy increase the levels of what peptide that binds and activates the same receptor as PTH?
PTHrP (PTH related peptide)
What are the levels of 1) PTH, 2) Ca2+, 3) Phosphate, 4) Vitamin D in patients with Humoral hypercalcemia of malignancy
1) Decreased
2) Increased
3) Decreased
4) Decreased
What autosomal dominant disorder is caused by mutations that inactive CaSR in parathyroid glands resulting in decrease of urinary calcium excretion and increase in serum calcium?
Familial hypocalciuric hypercalcemia (FHH)
What are the levels of 1) PTH, 2) Serum Ca2+, 3) Urine Ca2+, 4) Phosphate 5) Vitamin D in patients with Familial hypocalciuric hypercalcemia (FHH)?
1) Normal or increased
2) Increased
3) Decreased
4) Normal
5) Normal
What disorder presents with insufficient amount of calcium and phosphate available to mineralize growing bone and characterized by growth failure and skeletal deformities in children?
Rickets
What disorder presents with insufficient amount of calcium leading to new bone failing to mineralize and is characterized by bending and softening of weight-bearing bones in adults?
Osteomalacia
What is decreased with vitamin D-dependent rickets type 1?
1alpha-hydroxylase
What is decreased with vitamin D-dependent rickets type 2?
Vitamin D receptor
Both rickets and osteomalacia are characterized by?
Vitamin D deficiency
PTH, estrogen, calcitonin, or RANKL inhibitors can all be used to treat?
Osteoporosis