Parathyroid and Calcium Flashcards by John Caroccio

How much calcium does the body contain and where is it stored?

1-2 kg of calcium
98% in skeleton
0.03% Plasma
0.1% ECF
1% ICF

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What forms is Plasma calcium present in?

50% Ionized (active form)
41% Protein bound
9% Combined with anions

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Which protein is plasma calcium mostly bound to?

Albumin

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Does Ca+ equilibrate between skeleton and plasma?

Yes, but only 0.5% of bone in calcium is readily exchangeable

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What changes can be seen in hypocalcemia?

Tetany
Seizures
Longer QT
Nervous system excitement

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What two tests can be done to check for hypocalcemia?

Carpopedal spasm (tap on wrist)
Chvosteks sign (tap facial nerve)

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What can Longer QT lead to?

R on T phenomenon which can turn in Torsades

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What changes can be seen with hypercalcemia?

Nervous system depression
Short QT
Long PR
Constipation
Anorexia

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What is the CHIEF manifestation of hypercalcemia?

Skeletal muscle weakness

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What is treatment for hypercalcemia?

Maintain Urine ouput
Hydrate
Administer Mithramycin

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How much phosphorus is contained in the body and where can it be found?

1kg of phosphrous
85% skeleton
15% Muscle/tissue
1% ECF

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How much phosphorous is protein bound?

12%

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Do phosphorous levels or calcium levels fluctuate more significantly?

Phosphorus; moves between ECF and bone as well as between ECF and ICF

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How does phosphorus enter the ECF?

via GI, ICG, bone

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How does phosphorus leave the ECF?

via Urine, ICF, Bone

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Where is the major control site of phosphorus?

Kidneys

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Why does hypophosphatemia lead to weakness?

ATP is built on phosphorus

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How can GI absorption of phosphorus be increased?

1,25 D3

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PTH increase or decrease urinary excretion of phosphorus?

Increases

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What two cells are mainly contained in the parathyroid glands?

Chief and oxyphil cells

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Which cells secrete parathyroid hormone (PTH)?

Chief cells

What three things can cause enlargement of the parathyroid glands?

Prolonged stimulation
Pregnancy
Lactation

Is the parathyroid system made of negative or positive feedback system?

Negative feedback system

What is the most important hormone for calcium homeostasis?

Parathyroid Hormone (PTH)

Where in the kidney is calcium reabsorbed?

Proximal tubules

What is bone resorption?

Moving calcium from bone into blood

What are the 4 actions of PTH?

1. Increases bone resorption of Ca++ and Phos 2. Increases reabsorption of Ca++ in kidney 3. Decreases reabsorption of Phophate in renal tubules 4. Increases production of 1,25 Dihydroxycholecalciferol.

What is the major stimulus for PTH secretion?

Low serum Ca++ levels

What is the most common form of calcium in the body?

1,25 dihydroxycholecalciferol

Increased PTH causes what changes to calcium and phosphate?

Serum: Calcium up, Phosphate down Urine: Calcium down, Phosphate Up

What hormone opposes the effects of PTH?

Calcitonin

Where is calcitonin produced?

Parafollicular (c cells) of the thyroid

Increased calcitonin causes what changes to calcium and phosphate?

Serum: Calcium down, Phosphate down Urine: Calcium up, Phosphate up

What stimulus causes increased secretion of calcitonin?

Increased serum Ca++

What is the name of Vit D's active product?

1,25 Dihydroxycholecalciferol

How does Vitamin D effect serum or bone calcium levels?

Increases calcium absorption from the GI tract.

Where is Vitamin D3 formed?

Skin by exposure to sunlight

Where is Vitamin D converted to its active form?

the liver

Bone resorption of calcium is increased by ____ and inhibited by _____?

PTH | Calcitonin

Hypoparathyroidism results in what?

1. Tetany 2. Muscle cramps 3. Grand mal seizures 4. CV collapse

What is tx for hypoparathyroidism?

PTH, calcium, and Vit d supplementation

What airway related issue can hypoparathyroidism cause?

Laryngospasm d/t hypocalcemia

What other electrolyte disorder can cause calcium resistant hypocalcemia?

Hypomagnesemia ( treat mag first, then calcium.)

What are signs of primary hyperparathyroidism?

1. Hypercalcemia 2. Hypercalciuria 3. Hypophosphatemia 4. Hyperphosphaturia 5. Bone demineralization 6. Kidney stone formation 7. Cardiac function effected with short QT, depresses relaxation).

What is the most common cause of hyperparathyroidism?

Parathyroid hyperplasia and Parathyroid tumor

What is osteomalacia?

Softening of bones

Vit D deficiency in children results in what?

Rickets--- bones fail to mineralize

Calcium is indicated for treatment of _______ induced EKG changes because of its cell membrane stabilizing effects?

Hyperkalemia

What is the Calcium Chloride to Calcium Gluconate exchange rate?

1g Calcium Chloride= 3g Calcium Gluconate

Which patient is Calcium treatment contraindicated in?

Digoxin toxicity d/t risk of lethal arrhythmias