Metabolism of calcium, phosphate and magnesium

Question 1

how does PTH control calcium levels?

Answer 1

when calcium levels are low, it will:

1. act on the bone to release calcium
2. acts on the kidneys to activate vitamin D and thus indirectly causes ↑ GI reabsorption of calcium
3. in the kidney PTH will cause ↑ calcium reabsorption @ DCT and ↓ phosphate and bicarbonate reabsorption

PTH = Phosphate Trashing Hormone

Question 2

what is the difference between secondary and tertiary hyperparathyroidism

Answer 2

• secondary: reaction of the parathyroid glands to a hypocalcemia caused by something other than parathyroid pathology
• tertiary: PTH ↑ to maintain normocalcemia in the setting of vitamin D deficiency and then eventually PTH secretion becomes independent of calcium levels (usually occurs in settings of chronic renal failure)

Question 3

what is a congenital disorder that presents with congenital absence of parathyroid glands

Answer 3

Di George syndrome; it can also cause underdevelopment of the thymus and have congenital heart defects

Question 4

what is the issue in pseudohypoparathyroidism? What is the level PTH in these patients

Answer 4

↓ responsiveness of target organs due to problems of the PTH receptors
↑ PTH

Question 5

discuss the effects of other ion levels that can be caused by hypomagnesemia

Answer 5

hypocalcemia and hypophosphatemia and hypokalemia

Question 6

what level of phosphate would you expect to see in chronic alcohol abusers?

Answer 6

HYPOphosphatemia

Question 7

what are the two more serious complications of severe phosphate deficiency?

Answer 7

• respiratory failure

- rhabdomyolysis that can lead to acute renal failure

Question 8

hemolysis is a feature of low levels of: ________ (calcium, magnesium, phosphate)
why?

Answer 8

phosphate; depletion of 2,3 Diphosphoglycerate

Question 9

how does a artifactual cause of hyperphosphatemia present

Answer 9

hemolysis or delay in separation of blood samples

Question 10

chronic renal failure can chase hypo/hyper phosphatemia

Answer 10

hyperphosphatemia

Question 11

↑/ ↓ levels of PTH can cause HYPERphosphatemia

Answer 11

↓

Question 12

what are main cause of HYPOmagenesemia

Answer 12

malabsorption, malnutrition, alcoholism, chronic mineralocorticoid excess

Question 13

how does hypomagenesemia present

Answer 13

tetany, agitaiton, tremors, and convulsions

Question 14

_______ is the most important cause of hypermagnesemia

Answer 14

renal failure

Question 15

respiratory paralysis and cardiac arrest are major effects of _____magnesemia (hyper/hypo)

Answer 15

hypermagnesemia

Question 16

hypoalbuminemia will cause a low total plasma________ (ion)

Answer 16

↓ calcium but the ionized calcium level will be normal

Question 17

teatny is a feature of hyper/hypocalcemia

Answer 17

hypocalcemia

Question 18

it is important to have normal _______ levels in order to have regular absorption of calcium and phosphate

Answer 18

magnesium

Question 19

↑ phosphate levels are seen in what cause of hypercalcemia

Answer 19

excess vitamin D

Question 20

↑/ ↓ phosphate levels are seen in primary hyperparathyroidism

Answer 20

↓

Question 21

bisphosphonates are used to treat _______

Answer 21

hypercalcemia

Question 22

what is the first step in managing hypercalcemia?

Answer 22

correct dehydration by giving fluids because this will all for renal excretion of calcium

Question 23

PTH release is regulated primarily by serum Ca2+ and _______ concentrations.

Answer 23

Mg2+

Question 24

treatment of DKA Is associated with what metabolic abnormality

Answer 24

hypophosphatemia because it causes ↑ cellular uptake

Question 25

↓ _______ causes ↓ 2,3 disphosphogylcerate

Answer 25

phosphate