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SU 17: Wine regions of South America > Endocrine Lecture 5: Calcium and Parathyroid > Flashcards

Endocrine Lecture 5: Calcium and Parathyroid Flashcards

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1
Q

What functions in the body does Calcium contribute to?

A
  • Nerve conduction
  • Bone formation
  • Muscle function
  • Blood coagulation (factor IV is Ca ion)
  • Cerebral and cardiac function Capillary permeability
  • Cell growth and division
  • Neurotransmitter action
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2
Q

Where and in what ways is Ca stored or present in the body?

A

Body contains 1-2 kg of calcium

  • 98% in skeleton
  • 1% in cells
  • 0.1% in ECF
  • 0.03% in plasma
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3
Q

Plasma Ca is present in the following forms in the body:

A

-50% Ionized (active form)
Most important form for calcium functions on heart, the nervous system, and bone formation

-41% protein bound (primarily albumin)

-9% combined with anions (diffusible)
Equilibrates with bone Ca++, but only 0.5% of bone calcium is readily exchangeable
Rest is slowly exchangeable

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4
Q

How does HYPOcalcemia manifest?

A

Nervous system excitement
• Increased neuronal permeability to Na, easy action potentials • 50% ion/ 35% total decrease leads to spontaneous discharges • Tetany, seizures
– Most common in hand: carpopedal spasm
-Or face:Chvosteks sign:tapping facial nerve leads to twitching

• Longer QT

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5
Q

How does HYPERcalemia manifest?

A

Chief manifestation is skeletal muscle weakness
– Nervous system depression
• Short QT, long PR interval, constipation, anorexia
– Treatment:
• Maintain UOP, hydrate, administer mithramycin in severe cases

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6
Q

Where and in what ways is Phosphorus stored or present in the body?

A

Body contains 1 kg of phosphorus
• 85% skeletal, 15% muscle/tissue, 1% ECF
– Circulates in plasma 12% protein bound
– Levels fluctuate significantly more than Ca++ because Ph moves between ECF and bone as well as between ECF and ICF

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7
Q

Where is the major control site of Phosphorus balance?

A 
Major control site is kidney:
– Urinary excretion balances GI intake
– PTH increases urinary excretion 
    • Calcitonin to a lesser extent
– GI absorption increased by 1,25 D3
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8
Q

The Parathyroid consists of __ glands located behind the upper and lower poles of the ___ gland.

A

4

Thyroid

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9
Q

The Parathyroid glands are very small, they contain mainly ___ cells and ___ cells.

A

Chief and oxyphil cells

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10
Q

Chief cells secrete _____.

A

Parathyroid Hormone

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11
Q

Synthesis and secretion of parathyroid hormone is related to _____ concentrations in the blood.

A

Calcium

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12
Q

These 3 conditions can cause enlargement of the parathyroid gland:

A

Prolonged stimulation

Pregnancy

Lactation

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13
Q

Decreases in ECF concentration of ____ increases the secretion of Parathyroid Hormone (PTH)

A

Calcium

Likewise:

Increases in calcium concentration in the extracellular fluid decreases the activity of the parathyroid gland

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14
Q

Vitamin D (Cholecalciferol) and Calcitonin both help with reabsorption of Ca from the ______ of the kidney?

A

Proximal tubules

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15
Q

What are the main actions of PTH?

A
  • Major stimulus is low serum Ca++ level
  • Increases bone resorption to mobilize calcium and phosphate

-Increases reabsorption of Ca++ in the kidney’s distal tubules
• Decreases reabsorption of phosphate in the renal tubules
• Increases the production of 1,25-dihydroxycholecalciferol

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16
Q

Increased release of PTH results in:

A

-Increases the excretion of phosphate, potassium, and sodium by increasing the calcium/magnesium/hydrogen reabsorption
(largely in the distal tubules and collecting ducts)

Serum: Increased calcium, decreased phosphate

Urine: Decreased calcium, increased phosphate

17
Q

Where is Calcitonin produced?

A

parafollicular (clear or C cells) of the thyroid

18
Q

What are the main effects of Calcitonin?

A

-In general it has the opposite effect of parathyroid hormone

Secretion is controlled by serum calcium level
• Increased Ca++ leads to in creased secretion

Serum:
– Decreased calcium
– Decreased phosphate

Urine:
– Increased calcium excretion
– Increased phosphate excretion

19
Q

What is the active form of Vitamin D and how/where is it converted to it’s active form?

A

Vitamin D is not itself an active substance, but must be converted to its active product 1,25-dihydroxycholecalciferol

Vitamin D3 is converted to 1,25-dihydroxycholecalciferol by the liver

20
Q

What are the main functions of vitamin D (D3/1,25-dihydroxycholecalciferol)?

A

Vitamin D has a potent effect to increase calcium absorption from the intestinal tract

Vitamin D has important effects on both bone deposition and bone absorption

GI absorption of Ca++ is increased by Vitamin D

21
Q

Calcium regulation:

Urinary excretion of Ca is decreased by ____ and increased by ____.

A

decreased by PTH (parathyroid hormone)

increased by calcitonin

22
Q

Calcium regulation:

Bone respiration is increased by _____ and inhibited by _____.

A

Increased by PTH

inhibited by Calcitonin

23
Q

What is the primary cause of HYPOparathyroidism?

A

Usually a result of surgical damage to the gland during thyroid surgery
Calcium levels fall below normal in 24-72

24
Q

surgical damage to the parathyroid gland during thyroid surgery causes Calcium levels to fall below normal in 24-72 hours which results in:

A
  • Tetany: calcium ion interferes with membrane transport and interferes with the relaxation of the muscle
  • Muscle cramps
  • Grand mal seizures
  • Cardiovascular collapse
25
Q

Treatment for Hypocalcemia related to impaired PTH production:

A

PTH – expensive, short half life High calcium and Vit D intake
Occasionally 1/25-D3 necessary

  • Hypomagnesemia can cause hypocalcemia resistant to calcium
  • Must treat first with magnesium
  • Magnesium suppresses the release of PTH
26
Q

What is Primary Hyperparathyroidism?

A

Primary: inappropriate hypersecretion of PTH resulting in hypercalcemia

Results in hypercalcemia, hypercalciuria, hypophosphatemia, hyperphosphaturia, bone demineralization
Effects cardiac function (shortens QT interval, depresses relaxatioin)
Causes Kidney stone formation as Ca++ mobilized from bone must eventually be excreted by kidneys

Most common cause of hyperparathyroidism is parathyroid hyperplasia or parathyroid tumor
Pregnancy may stimulate the parathyroids

27
Q

What is Secondary Hyperparathyroidism?

A

Hyper secretion of PTH in response to a hypocalcemic stress examples: Vitamin D deficiency and Chronic renal disease

• Results in osteomalacia
– Inadequate mineralization of the bones

28
Q

Vitamin D deficiency in children manifests as:

A

Rickets – bones fail to mineralize, epiphyses fail to fuse, epiphyseal plates widen and bowing and fractures occur


29
Q

Vitamin D deficiency in adults manifests as:

A

osteomalacia- inadequate mineralization of the bones

30
Q

Sources of Vitamin D deficiency:

A

Inadequate dietary intake
Often due to fat malabsorption syndrome

Inadequate sunlight

Decreased absorption of calcium and phosphate, decreased serum calcium and phosphate, increased PTH and increased bone resorption

31
Q

One gram of Calcium Chloride contains the equivalent amount of ionized calcium as __ grams of Calcium Gluconate

A

3

32
Q

_____ is indicated for treatment of hyperkalemia induced EKG changes because of its cell membrane stabilizing effects.

A

Calcium

33
Q

Calcium is indicated for treatment in patients with hypotension associated with either ____ ____ ___ or beta adrengergic blockers.

A

Calcium Channel Blockers

34
Q

The treatment for Magnesium toxicity associated with treatment of preeclampsia is:

A

Calcium

35
Q

Calcium is contraindicated in patients with ____ toxicity as it may cause lethal arrhythmias.

A

Digoxin

Digibind is an immunoglobulin fragment that binds with digoxin. It is currently considered first-line treatment for significant dysrhythmias (eg, severe bradyarrhythmia, second- or third-degree heart block, ventricular tachycardia or fibrillation) from digitalis toxicity.

SU 17: Wine regions of South America (10 decks)

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