Disorders of Calcium Metabolism

Question 1

PTH increases serum calcium by four ways: _________________.

Answer 1

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

Question 2

What is the major storage form of vitamin D?

Answer 2

25-hydroxy vitamin D (in the liver)

Question 3

What enzyme in the kidney activates vitamin D?

Answer 3

1-alpha hydroxylase

Question 4

To assess for deficiency, we measure ________________.

Answer 4

the storage form of vitamin D

Question 5

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

Answer 5

Vitamin D increases phosphate levels, while PTH decreases phosphate levels

Question 6

What are the two most common causes of hypercalcemia?

Answer 6

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

Question 7

What are some less common causes of hypercalcemia?

Answer 7

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

Question 8

What is the first step in evaluating hypercalcemia?

Answer 8

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

Question 9

What are brown tumors?

Answer 9

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

Question 10

Most people with hyperparathyroidism have what symptoms?

Answer 10

None, most are asymptomatic

Question 11

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

Answer 11

Anemia (because PTH suppresses erythropoiesis)

Question 12

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

Answer 12

Chondocalcinosis

Question 13

Most of the cases of hyperparathyroidism are ___________.

Answer 13

sporadic (10%)

Question 14

MEN I is the disorder of three Ps: __________________.

Answer 14

pituitary adenoma, pancreatic endocrine tumors, and hyperParathyroidism

Question 15

What is the genetic cause of MEN I?

Answer 15

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

Question 16

Adenomas can be treated by _____________.

Answer 16

removing one gland –the affected gland

Question 17

Parathyroid hyperplasia is treated by ______________.

Answer 17

removing three glands

Question 18

What medical options can treat primary hyperparathyroidism?

Answer 18

Calcimimetics to decrease release of PTH

Question 19

What three things can cause the release of PTH?

Answer 19

Decreased Ca
Increased PO4
Decreased vitamin D

Question 20

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

Answer 20

Lung
Breast
Head and neck

Question 21

What is the most common mediator of hypercalcemia from malignancy?

Answer 21

PTH-related peptide (PTH-RP)

Question 22

How can you differentiate primary hyperparathyroidism and familial hypocalciuric hypercalcemia?

Answer 22

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

Question 23

What causes FHH?

Answer 23

Defects in the sensor regions of the calcium sensors.

Question 24

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

Answer 24

Hypoparathyroidism

Question 25

How do you correct calcium if albumin is low?

Answer 25

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

Question 26

Those with renal disease are deficient in ________________.

Answer 26

the active form of vitamin D

Question 27

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

Answer 27

Autoimmune hypoparathyroidism

Question 28

What causes pseudohypoparathyroidism?

Answer 28

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

Question 29

True or false: vitamin D promotes bone resorption.

Answer 29

True! At high levels vitamin D can stimulate osteoclasts.

Question 30

What three cell types have CaSRs?

Answer 30

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

Question 31

Hyperparathyroidism is most often _______________.

Answer 31

asymptomatic

Question 32

Many ____________ patients don’t need surgery.

Answer 32

primary hyperparathyroidism

Question 33

What two lab criteria are diagnostic of secondary hyperparathyroidism?

Answer 33

• High PTH

- Low Ca, low vitamin D, or high phosphate

Question 34

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

Answer 34

hypocalcemia; hyperphosphatemia