calcium homeostasis - notes

Question 1

essential physiological roles of calcium

Answer 1

1: muscle contraction
2: neural excitation
3: enzyme cofactor
4: cellular secretion
5: structural role in bone

Question 2

essential physiological roles of phosphorus

Answer 2

1: intermediate metabolism
2: atp
3: structural role in bone

Question 3

symptoms of hypocalcemia

Answer 3

1: hyperexcitability
2: paresthesias/tingling
3: muscle cramps
4: tetany
5: seizures
6: signs: chvestok and trousseau

Question 4

hypercalcemia

Answer 4

1: hypoexcitability
2: lethargy
3: confusion
4: coma
5: no specific signs

Question 5

effects of albumin levels on Ca

Answer 5

increased albumin => total Ca increases, ca2+ doesn’t change

decreased albumin => total Ca decreases, free ca doesn’t change

Question 6

effects of pH on Ca levels

Answer 6

increased pH => total Ca doesn’t change but free Ca goes down
decreased pH => total ca doesn’t change but free ca goes up

Question 7

hormones involved in ca regulation

Answer 7

parathyroid hormone
vitamin D metabolites
calcitonin

Question 8

1,25(OH)2D

Answer 8

active vitamin D metabolite that mediates 90% of ca absorption
in duodenum and jejunum
(rest of Ca absorbed by passive diffusion)
also controls 10% of PO4 absorption

Question 9

PO4 absorption

Answer 9

90% passive

10% controlled by 1,25(OH)2D

Question 10

factors increasing bone resorption

Answer 10

1: parathyroid hormone (resorption and turnover)
2: parathyroid hormone-related peptide
3: cytokines and growth factors
4: excess thyroid hormones
5: excess 1,25 vitamin D or vitamin A

Question 11

factors decreasing bone resorption

Answer 11

1: estrogens and SERMS (selective estrogen receptor modulators
2: bisphosphonates - eg alendroate (fosamax)
3: calcitonin (weak)

Question 12

factors increasing bone formation

Answer 12

parathyroid hormone (formation and turnover)

Question 13

hormonal factors affecting renal ca handling

Answer 13

parathyroid hormones => decreased ca excretion

glucocorticoids => increased ca excretion

Question 14

dietary factors affecting renal ca handling

Answer 14

sodium => increased ca excretion

protein => increased ca excretion

Question 15

drugs affecting renal ca handling

Answer 15

furosemide => increased ca excretion

hydrochlorothiazide => decreased ca excretion

Question 16

activity level effects on renal ca handling

Answer 16

inactivity => increased ca excretion

Question 17

factors that increase ca excretion via renal ca handling

Answer 17

glucocorticoids
dietary sodium and protein
furosemide
inactivity

Question 18

factors that decrease ca excretion via renal ca handling

Answer 18

parathyroid hormone

hydrochlorothiazide

Question 19

factors affecting vitamin D3 production

Answer 19

degree of skin pigmentation

amount of sunlight or uv exposure

Question 20

regulation of vitamin D metabolism

Answer 20

25-hydroxylase in liver unregulated - 25(OH)D levels indicative of general vitamin D status
1-hydroxylase in renal proximal tubular cells highly regulated

Question 21

regulation of 1-hydroxylase

Answer 21

PTH stimulates
low ca stimulates
low PO4 stimulates
1,25(OH)2D inhibits (directly and indirectly via PTH)