Flashcards in Hormonal Control of Calcium and Phosphate Metabolism Deck (28):
What functions does calcium participate in?
1. Nerve function
2. Muscle contraction
3. Blood clotting
4. Bone and teeth
what functions does phosphate participate in?
2. Biological buffer
Where is most calcium stored?
Where is most phosphorous stored?
Intracellularly and bone
How is phosphate brought into the body?
How is phosphate excreted?
What 3 hormones regulate calcium?
2. 1,25 Dihydroxycholecalciferol: calcitriol
What cells release PTH?
Chief cells of the parathyroid
When is PTH released? What does it do?
1. When calcium levels are low (below 8.5 mg/dL), detected by the parathyroid gland
2. PTH secreted into the blood
3. PTH reaches target organs
A. osteoclasts resorb bone
B. Kidney retains Calcium and promotes activation of an inactive form of vitamin D to an active form of vitamin D
C. Small intestine increases absorption of more calcium under the influence of calcitriol
4. Calcium Levels rise and inhibit PTH
What coenzyme helps facilitate absorption of calcium and phosphate in the intestine?
1. Vitamin D
Where is vitamin D activated?
1. Formation and hydroxylation of vitamin D3. 25-Hydroxylation takes place in the liver, and the other hydroxylations (1, 25-hydroxy D3) occur primarily in the kidneys.
What are the sources of vitamin D?
2. Diet and supplementation of D3 and D2
Where is calcitonin produced?
Produced by parafollicular cells of thyroid gland
What is the stimulus for calcitonin release?
Secreted in response to increased plasma calcium levels above 11 mg/dL for adults
What is the function of calcitonin?
1. Lowers circulating plasma calcium and phosphate levels
A. Inhibits bone resorption
B. Increases Ca excretion
1. Excessive PTH secretion that results in:
A. Increased plasma calcium level
B. Decreased plasma phosphate level
Why is hypercalcemia a problem?
1. Excess Ca enters cells
2. Results in decreased membrane excitability
3. Effects cardiac muscle & nervous system
A. bradycardia, shortened Qt interval
B. Fatigue, confusion, decreased LOC
C. Constipation, anorexia
What can cause primary hyperparathyroidism?
What can cause secondary hyperparathyroidism?
Vitamin D deficiency or CRF
What are the sxs of hypercalcemia?
Bones, stones, thrones, abdominal groans, psychiatric moans, with fatigue overtones
What does (hypoparathyroidism) deficiency of PTH result in?
1. Decreased plasma calcium level
2. Increased plasma phosphate level
Why is hypocalcemia a problem?
1. Disturbances in cell membrane potential
2. Results in cardiac & neuromuscular irritability
What are the sxs of hypocalcemia?
D. Stridor & spasms
A. Lips, tongue, fingers & feet
3. Pos Chovstek’s Sign
4. Pos Trousseau Sign
When does hypocalcemia occur?
Following thyroid or parathyroid surgery
What causes RIckets disease and osteomalacia?
1. Caused by insufficient Vitamin D
A. Results in inadequate calcium and phosphate for bone mineralization
What are the sxs of childhood rickets?
1. Stunted growth
2. Severe bow-legged
What are the sxs of adult osteomalacia?
1. bone malformation