Calcium and Bone Disorders

Question 1

What is the pathway of Vitamin D in the body?

Answer 1

Vitamin D –> Liver –> Calcidiol25-0H-D –> Kidney + PTH –> Calcitriol1,25-OH2-D –> Small intestine, bone

Question 2

Low Ca + Low PTH –>

Answer 2

hypoparathyroidism

• -> PO4 will also be low (follows PTH)
• -> may be surgical or autoimmune

Question 3

What drug is a calcimimetic?

Answer 3

cinacalcet

use for non-surgical treatment of hyperparathyroidism

• -> lowers calcium
• -> lowers PTH
• -> DOES NOT improve BMD

Question 4

In cases of hypercalcemia or hypocalcemia, what is the first lab to check?

Answer 4

Parathyroidhormone

Question 5

Low Ca + High PTH + High PO4 –>

Answer 5

pseudohypoparathyroisism

–> decreased 1, 25 (OH)2D

Question 6

High calcium + High (normal) PTH –>

Answer 6

primary hyperparathyroidism

Question 7

How do you treat hypoparathyroidism?

Answer 7

Give calcium and calcitriol (activated Vitamin D)

Question 8

Complications of primary hyperparathyroidism

Answer 8

Signs/symptoms of hypercalcemia
Kidney stones, nephrocalcinosis, decline kidney function
Bone loss –> osteoporosis

Question 9

What will happen if you give calcidiol to a patient with hypoparathyroidism?

Answer 9

They will not be able to convert to active Vitamin D (calcitriol) without PTH

Question 10

High calcium + Low (appropriately) PTH –>

Answer 10

Not parathyroid gland disease

Other causes of high calcium:
PTH-rp cancer, excess 1,25OH2D cancer, direct osteolysis/cytokine cancer, granulomatous disease with excess 1,25OH2D, excess calcium intake, excess Vit D/A

Question 11

What is the effect of low/absent PTH on serum calcium?

Answer 11

Increased urinary calcium excretion (more pronounced with higher serum calcium) –> increase risk of kidney stones, nephrocalcinosis

Question 12

What is a benign cause of hypercalcemia?

Answer 12

Familial hypercalcemia hypocalciuria (reset of homeostasis)

caused by inactivating mutation of CaSR in PT, kidney

• -> ‘think’ there is low serum Calcium
• -> kidney holds Ca –> hypocalciuria
• -> PT increases PTH

Question 13

Low Ca + High PTH + Low PO4 + low calcidiol (25OHD) –>

Answer 13

Either Vitamin D resistance (high calcitriol) or Vitamin D deficiency (low calcitriol)

Question 14

How do you treat hyperparathyroidism?

Answer 14

Best: parathyroidectomy

Medical high calcium: cinacalcet (calcimimetic)
Medical osteoporosis: antiresorptive agent (bisphosphonate usually)
Medical kidney stones: diet modification, thiazides to decrease urinary Ca excretion, cinacalcet to control serum calcium

Question 15

Low Ca + High PTH + normal PO4 + normal Vitamin D (calcidiol, calcitriol) –>

Answer 15

Insufficient calcium intake

Question 16

High Ca + Low PTH + increased PTHrP –>

Answer 16

malignancy (lung, renal)

usually more severe than PHPT
most common inpatient cause of hypercalcemia

Question 17

What happens to PTH in the presence of low Vitamin D and low serum calcium?

Answer 17

Compensatory elevation of PTH

Ex. Vitamin D Deficiency

Question 18

Treatment of hypercalcemia of malignancy

Answer 18

fluids to dilute Ca, induce calciuresis
IV bisphosphonates
treat malignancy

Question 19

What would labs for primary hyperparathyroidism look like?

Answer 19

High Ca + High (normal) PTH + normal urine Ca

Question 20

How do you treat patients with Vitamin D deficiency?

Answer 20

Give vitamin D

–> able to activate in liver and kidney with normal parathyroid hormone

Question 21

If High Ca + Low PTH, what test would you follow with?

Answer 21

PO4 = phosphate