Disorders of Calcium Metabolism Flashcards

1
Q

PTH increases serum calcium by four ways: _________________.

A

increased bone resorption; increased intestinal absorption; decreased renal excretion; and increased renal resorption

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2
Q

What is the major storage form of vitamin D?

A

25-hydroxy vitamin D (in the liver)

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3
Q

What enzyme in the kidney activates vitamin D?

A

1-alpha hydroxylase

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4
Q

To assess for deficiency, we measure ________________.

A

the storage form of vitamin D

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5
Q

Vitamin D has a similar effect as parathyroid hormone. How do they differ?

A

Vitamin D increases phosphate levels, while PTH decreases phosphate levels

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6
Q

What are the two most common causes of hypercalcemia?

A

Primary hyperparathyroidism and malignancy (these account for 90% of hypercalcemias)

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7
Q

What are some less common causes of hypercalcemia?

A
Exogenous vitamin D toxicity
Exogenous vitamin A toxicity
Hyperthyroidism 
Granulomatous disease 
Thiazide diuretics
Milk-alkali syndrome 
Immobilization
Adrenal insufficiency
Acute renal failure 
Familial hypocalciuric hypercalcemia
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8
Q

What is the first step in evaluating hypercalcemia?

A

Measure PTH: there are only two disorders where it’s high (primary hyperparathyroidism and familial hypercalcemia)

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9
Q

What are brown tumors?

A

They are overgrowths of osteoclasts that occur in response to extremely elevated levels of parathyroid hormone (such as from a parathyroid adenoma)

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10
Q

Most people with hyperparathyroidism have what symptoms?

A

None, most are asymptomatic

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11
Q

What might you see in a CBC of someone with hyperparathyroidism?

A

Anemia (because PTH suppresses erythropoiesis)

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12
Q

Someone with primary hyperparathyroidism might have lines in their joint spaces. What are these?

A

Chondocalcinosis

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13
Q

Most of the cases of hyperparathyroidism are ___________.

A

sporadic (10%)

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14
Q

MEN I is the disorder of three Ps: __________________.

A

pituitary adenoma, pancreatic endocrine tumors, and hyperParathyroidism

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15
Q

What is the genetic cause of MEN I?

A

Defects in the Menin gene (MEN1n… get it?)

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16
Q

Adenomas can be treated by _____________.

A

removing one gland –the affected gland

17
Q

Parathyroid hyperplasia is treated by ______________.

A

removing three glands

18
Q

What medical options can treat primary hyperparathyroidism?

A

Calcimimetics to decrease release of PTH

19
Q

What three things can cause the release of PTH?

A

Decreased Ca
Increased PO4
Decreased vitamin D

20
Q

Which three cancers are the most common cause of hypercalcemia due to malignancy?

A

Lung
Breast
Head and neck

21
Q

What is the most common mediator of hypercalcemia from malignancy?

A

PTH-related peptide (PTH-RP)

22
Q

How can you differentiate primary hyperparathyroidism and familial hypocalciuric hypercalcemia?

A

Measure 24-hour urine calcium. In a patient with FHH, it will be low.

23
Q

What causes FHH?

A

Defects in the sensor regions of the calcium sensors.

24
Q

There is only one cause of hypocalcemia that presents with low PTH. What is it?

A

Hypoparathyroidism

25
Q

How do you correct calcium if albumin is low?

A

Add 0.8 [Ca] for every 1.0 unit of albumin below 4.0

26
Q

Those with renal disease are deficient in ________________.

A

the active form of vitamin D

27
Q

________________ usually presents with mucocutaneous candidiasis, low calcium, high phosphate, and low PTH.

A

Autoimmune hypoparathyroidism

28
Q

What causes pseudohypoparathyroidism?

A

Defects in the signal transduction from the PTH receptor (thus, they actually present with high PTH!)

29
Q

True or false: vitamin D promotes bone resorption.

A

True! At high levels vitamin D can stimulate osteoclasts.

30
Q

What three cell types have CaSRs?

A

Parafollicular thyroid cells, parathyroid chief cells, and proximal renal tubule cells

31
Q

Hyperparathyroidism is most often _______________.

A

asymptomatic

32
Q

Many ____________ patients don’t need surgery.

A

primary hyperparathyroidism

33
Q

What two lab criteria are diagnostic of secondary hyperparathyroidism?

A
  • High PTH

- Low Ca, low vitamin D, or high phosphate

34
Q

Hypoparathyroidism should be suspected when __________ is found in conjunction with ____________.

A

hypocalcemia; hyperphosphatemia