Calcium & bone problems

Question 1

How is parathyroid involved in calcium metabolism?

Answer 1

parathyroid hormone - maintains plasma calcium by direct actions on kidney, bone, and activating vit. D

Question 2

How is bone involved in calcium metabolism?

Answer 2

calcium and phosphorous depot. Active tissue - an increase in calcium removal leads to bone loss

Question 3

How is kidney involved in calcium metabolism?

Answer 3

~PTH affects calcium reabsorption/excretion at kidney.

~Activated vitamin D synthesis

Question 4

How is PTH involved in calcium metabolism?

Answer 4

Maintains serum calcium.
~Increase calcium and phosphate reabsorption from bone.
~Increases calcium reabsorption at the kidney.
~Increase phosphate excretion from kidney.
~Stimulates conversion of vitamin D to active form

Question 5

How is vitamin D involved in calcium metabolism?

Answer 5

25(OH)D3: storage

1,25(OH)2D3: active

Question 6

How is calcium absorbed from the GI tract?

Answer 6

Absorption from the GI tract:
Daily intake (≤ 200mg ≥ 1g)
Passive absorption:
Inefficient; only 10-20% absorbed passively
Active absorption:
Dependent on the active form of Vitamin
D=[1,25(OH)2D].

Question 7

What is the only reason to ever get a calcitonin test?

Answer 7

Elevated in Medullary Thyroid Carcinoma

Question 8

Where is calcitonin made and what is its function?

Answer 8

• Produced from the C-cells of the thyroid.

* Inhibits osteoclast (bone resorbing cell) activity.

Question 9

What other serum lab test do you need to get when you order a serum calcium?

Answer 9

albumin - most serum calcium is bound to albumin, not floating freely (ionized)

Question 10

What is a common cause of secondary hyperparathyroidism?

Answer 10

vitamin D deficiency:
low vitamin D, PTH rises to try to compensate and stimulate calcium absorption; also mobilizes calcium from bone
Primary clinical effect: bone loss

Question 11

What are the levels of PTH and calcium in primary hyperparathyroidism?

Answer 11

High PTH, High Ca2+

Question 12

What is Chvostek’s sign?

Answer 12

twitching of the ipsilateral facial muscle when
the facial nerve is gently tapped
(hypocalcemia)

Question 13

What are the neuromuscular symptoms of acute hypocalcemia?

Answer 13

– minor - paresthesias, numbness, tingling of the extremities
– major - carpal-pedal spasm, laryngospasm, seizures

Question 14

What is Trousseau’s sign?

Answer 14

carpal spasm after the blood pressure cuff is

inflated above the systolic pressure for 2 minutes (hypocalcemia)

Question 15

What medication can be used for hypocalcemia (besides calcium and vitamin D supplementation)?

Answer 15

thiazide diuretics - increase calcium reabsorption

Question 16

What are some uncommon causes of hypercalcemia?

Answer 16

– Hyperthyroidism
– Granulomatous disease (Sarcoid)
– Drugs (lithium, aluminum intoxication, thiazide diuretics, vitamin D, vitamin A)
– Immobilization
– Milk-alkali Syndrome

Question 17

What is the predominant presentation of Primary Hyperparathyroidism?

Answer 17

“asymptomatic” hypercalcemia

Question 18

What are the clinical manifestations of primary hyperparathyroidism?

Answer 18

Site specific relative bone loss compared with age, sex matched controls
Distal radius > hip > spine
Fracture risk increased: radius and spine

Question 19

What is the first treatment for hypercalcemia of malignancy?

Answer 19

Hydration! Volume depletion is a uniform manifestation

Question 20

Familial Hypocalciuric Hypercalcemia is a benign condition.

T/F

Answer 20

True

Question 21

Why is it important to distinguish FHH from primary hyperparathyroidism?

Answer 21

to avoid unnecessary parathyroidectomy

Question 22

You should get xrays in patients at risk for osteoporosis in order to check for bone density.
T/F

Answer 22

False.
• Plain films do not measure bone density. Could be used to look for fractures.
• Bone density and therefore fracture risk are
best measured with bone densitometry
measurements (DXA, Q-CT, etc)

Question 23

Indications for bone density test? (USPSTF)

Answer 23

~women aged 65 years or older
~younger women whose fracture risk is equal to or greater than that of a 65-year-old white woman who has no additional risk factors
~current evidence is insufficient to assess the balance of benefits and harms of screening for osteoporosis in men

Question 24

A bone density test is sufficient to check for suspected osteoporosis.
T/F

Answer 24

False.
You must assess the other clinical risk
factors for BOTH bone loss and fracture as well as work up the metabolic factors.

Question 25

Is one pill a week (bisphosphonate) enough to treat osteoporosis?

Answer 25

NO!

There must ALWAYS be calcium and vitamin D involved.

Question 26

What is the difference between osteomalacia and rickets?

Answer 26

Osteomalacia and rickets are the clinical
syndromes which result from inadequate bone
mineralization. “Rickets” is the term used to define the syndrome in children; “osteomalacia” is used to describe adults.

Question 27

What are the three etiologies of osteomalacia?

Answer 27

1. vitamin D deficiency
2. phosphate deficiency
3. inhibitors of mineralization (e.g. aluminum, fluoride)