Parathyroid

Question 1

when is parathyroid hormone secreted

Answer 1

when calcium is low, PTH stimulated. when calcium rises, PTH is suppressed

Question 2

classical actions of PTH

Answer 2

release Ca from bone, reabsorb Ca in kidneys. this leads to synth of 1,25 OH2 D3 and absorption of Ca and PO4 in small intestine.

Question 3

what accounts for most of the protein binding of calcium?

Answer 3

albumin! need to use a formula to correct calcium level.

corrected total calcium (mg/dL) = measured total calcium + 0.8X [4- measured albumin]

Question 4

phosphorus

Answer 4

levels influenced by PTH and 1,25(OH)2D. proximal tubule reabsorption increased by phosphate depletion, hyperparathyroidism, and hypocalcemia. excretion increased by PTH, PTHrP, hypercalcemia, hypokalemia, hypomagnesemia, calcitonin, glucocorticoids and diuretics

Question 5

magnesium

Answer 5

necessary for release of PTH and for the action of the hormone of its target tissues. primarily renally excreted. some drugs, furosemide and cisplatin, inhibit magnesium reabsorption at the loop of henle.

Question 6

vitamin D

Answer 6

maintains normal serum calcium level by increasing intestinal absorption of dietary calcium and stimulating bone cells to become osteoclasts.

Question 7

hypercalcemia

Answer 7

most common causes are hyperparathyroid or malignancy. if primary hyperparathyroid, PTH level is high or normal.

Question 8

primary hyperparathyroidism

Answer 8

results from excessive PTH secretion. usually caused by an adenoma. diagnosed with an elevated calcium, elevated or normal PTH, may see low phosphorus, elevated urine calcium.

Question 9

treatment of primary hyperparathyroidism

Answer 9

cured when abnormal tissue is removed. surgery usually good. those with mild disease or asymptomatic could be followed.

Question 10

medical treatment of primary hyperparathyroidism

Answer 10

adequate hydration and ambulation. moderate calcium intake. bisphosphonates may be useful to treat low bone density. calcomimetics can reduce PTH and Ca levels. sensipar is FDA approved for hyperparathyroid in renal disease and parathyroid carcinoma and in ppl who refuse surgery

Question 11

treatment of hypercalcemia

Answer 11

diagnose and treat underlying cause and mechanism. mild (14): can be life threatening, rquires immediate treatment, prognosis may be poor if from malignancy

Question 12

bisphosphonates

Answer 12

inhibits bone resorption, need to be given IV for this. pamidronate and zoledronic acid most common. does not work immediately. can cause fever/flu like symptoms.

Question 13

calcitonin

Answer 13

modest yet rapid lowering of Ca. increases urinary calcium excretion, inhibits bone resorption. good for acute setting

Question 14

secondary hyperparathyroidism

Answer 14

PTH secreted in response to perceived low calcium concentration. occurs in renal disease due to phosphate retention and lack of 1-alpha hydroxylase activity, resulting in a deficient 1,25 (OH)2D. vitamin D deficiency can be a cause.

Question 15

tertiary hyperparathyroidism

Answer 15

result of parathyroid glands becoming autonomous after prolonged secondary hyperparathyroidism. calcium is elevated.

Question 16

hypocalcemia

Answer 16

can arise from destruction or failuure of the parathyroid glands or inactivity of PTH at target tissues. hypocalcemic disorders can be categorized based upon low or elevated PTH levels.

Question 17

chronic renal failure and hypocalcemia

Answer 17

most common cause of hypocalcemia where phosphorus, PTH, and creatinine levels are high. limited excretion of Phosphorus and diminished hydroxylation of 1,25 vitamin D causes decreased Ca absorption and decreased mobilization from bone which causes PTH secretion. treat with calcitriol or other vitamin D analogs. can use phosphate binders or calcimimetics

Question 18

hypoparathyroidism

Answer 18

when PTH produced is insufficient to maintain serum calcium levels or is unable ot function properly at target tissues. usually low Ca, high phosphorus, and low PTH.

Question 19

25-hydroxyvitamin D as a pharm agent

Answer 19

aggressive repletion necessary in patients with vit D deficiency secondary to dietary insufficiency. Vit D deficiency can present with a low Ca and phosph, high PTH and/or low AP, low urine Ca.

Question 20

hypophosphatemia

Answer 20

caused by decreased intestinal absorption, increased urinary losses, or transcellular shift. treat with replacing phosphorus and calcitriol

Question 21

bisphosphates to treat osteoporosis

Answer 21

reduce osteoclast bone resorption with an increase in BMD and a decrease in fracture risk. alendronate, risedronate, and ibandronate. can lead to GI irritation at esophagus. take when fasting.

Question 22

SERMs for treatment of osteoporosis

Answer 22

selective estrogen receptor modulators. use in postmenopausal women. estrogen like compounds, cause decrease in bone resorption. doesnt have same undesireable effects as estrogen. raloxifene.

Question 23

teriparatide for osteoporosis

Answer 23

only anabolic agent for osteoporosis. PTH analog. reserved for patients at high risk of fracture. given as daily shot. up to 2 years.

Question 24

denosumab for osteoporosis

Answer 24

RANK ligand inhibitor. antiresorptive. very well tolerated, can lead to skin infections or hypocalcemia

Question 25

paget’s disease of bone

Answer 25

localized disorder of bone remodeling. increase in osteoclast mediated bone resoprtion and in bone formation, leads to disorganized bone. use bisphosphonates to treat. can use calcitonin in patients with renal insufficiency.

Question 26

osteogenesis imperfecta

Answer 26

heritable disorder of type 1 collagen. can cause osteopenia, bone fractures, skeletal deforminty. treat with bisphosphonate.