Parathyroids and Bone

Question 1

What are the actions of PTH?

Answer 1

• releases Ca from bone
• reabsorbs Ca in kidneys
• synthesis of 1,25 (OH)2 D3
• increases phosphate excretion

Question 2

What is the name of the bone involvement with hyperPTH?

Answer 2

• osteitis fibrosis cystica

Question 3

Besides surgery to remove the abnormal tissue, what are the treatment options for primary hyperPTH?

Answer 3

• adequate hydration and encourage movement
• moderate calcium intake
• bisphosphonates (inhibit bone breakdown)
• calcimimetics (alter function of calcium sensing receptor)

Question 4

Secondary hyperPTH is often caused by renal failure. What are the treatment options?

Answer 4

• low phosphate diet
• phosphate binders (calcium carbonate, calcium acetate, sevelamer)
• replacement of 1,25 vitamin D (calcitriol, paracalcitol, doxercalciferol)
• calcimimetics (cinacalcet)
• dialysis

Question 5

What are the most common causes of hypercalcemia? What is your first step and how do you interpret the results?

Answer 5

• most commonly from hyperparathyroidism or malignancy
• order PTH level
• if PTH is low, seek out other information including PTHrP (malignancy), vit D levels (increased in sarcoid or TB), 24 hr urine calcium (low in familial hypocalciuric hypercalcemia)
• if PTH is high, look into primary or secondary hyperparathyroidism

Question 6

What is the most common cause of primary hyperparathyroidism?

Answer 6

• benign solitary adenoma

- will see high Ca, high PTH, low phosphorus, high urine calcium

Question 7

What is the use of diuretics in hypercalcemia?

Answer 7

• use loops (with adequate fluid hydration) to increase urinary calcium excretion

Question 8

What is the downside of using calcitonin to treat hypercalcemia?

Answer 8

• repeated exposure can lead to downregulation of calcitonin receptors and cause tachyphylaxis in 2-3 days
• this makes this drug much better for the acute setting

Question 9

What is the use of corticosteroids in hypercalcemia treatment?

Answer 9

• blocks vit D production

- used in vit D intoxication, granulomatous disease, and hematologic malignancies

Question 10

What is the pathogenesis of secondary hyperparathyroidism due to renal failure?

Answer 10

• there is a perceived low calcium concentration due to phosphate retention and lack of 1-alpha hydroxylase activity in the kidney (deficient 1,25(OH)2D)
• phosphorus directly stimulates PTH at high concentrations
• treat with vit D replacement, low phosphate diet, phosphate binders, and dialysis

Question 11

When you see a patient with hypocalcemia, what other tests should you run?

Answer 11

• check albumin level
• check magnesium level
• phosphorus and creatinine levels will also help

Question 12

What drugs can be used as vitamin D replacements in the setting of chronic renal failure?

Answer 12

• calcitriol, paracalcitol, and doxercalciferol because they do not require activation in the kidney to work

Question 13

What are the three phosphate binders?

Answer 13

• sevelamer, calcium carbonate, calcium acetate

Question 14

What are the lab levels in hypoparathyroidism?

Answer 14

• low PTH, low calcium, high phosphorus

- in pseudohypoparathyroidism, PTH levels will be elevated

Question 15

What T score indicates osteoporosis?

Answer 15

• less than -2.5

Question 16

What are the treatment options for postmenopausal women with osteoporosis?

Answer 16

• bisphosphonates (“drones”)
• SERMs (“fenes,” mostly raloxifene)
• calcitonin (weirdly, has an analgestic effect on acute vertebral fractures)
• teriparatide (PTH analog, anabolic, small bursts stimulate osteoblasts)
• denosumab (RANK ligand inhibitor)

Question 17

What future treatments are on the horizon for treating osteoporosis?

Answer 17

• other anabolic agents
• cathepsin K inhibitors
• sclerostin pathway

Question 18

What is Paget’s disease of the bone?

Answer 18

• localized disorder of bone remodeling, with a disorganized base
• leads to pain, discomfort, and deformities
• treat with bisphosphonates or calcitonin