Lecture 9 - Calcium I

Question 1

Calcium composition in body?

Answer 1

40% ion form, 50% protein bound (albumin) and 10% complexed with anions

Question 2

Parathyroid hormone?

Answer 2

secreted by chief cells of parathyroid gland when serum Ca drops, binds to PTH receptor 1

Question 3

PTH functions?

Answer 3

oesteoclastic bone reabsorption, renal tubular reabsorption of Ca, renal hydroxylation of 25 (OH)D

Question 4

Vitamin D effect?

Answer 4

skin absorption activates liver production of 25 (OH)D, which stimulates PTH production

Question 5

PTHrP?

Answer 5

parathyroid hormone related peptide, paracrine regulator of breast, bone and skin development, produced in excess by epithelial cell tumours

Question 6

PTH dependent hypercalcaemia?

Answer 6

high serum calcium with high PTH, primary hyperthyroidism or CaSR mutation

Question 7

PTH independent hypercalcaemia?

Answer 7

high serum calcum without high PTH, cancer (PTHrP) or vitamin D cause (sarcoidosis)

Question 8

Causes of hypocalcaemia?

Answer 8

hypoparathyroidism, PTH resistance, abnormalities of Vitamin D metabolism

Question 9

Main factors involved in phosphate balance?

Answer 9

diet, flux from EC to ICF, kidney

Question 10

Causes of hyperphosphatemia?

Answer 10

increased input (IV phosphate, cell death) and decreased excretion (renal failure PTH deficiency or resistance)

Question 11

Causes of hypophosphatemia?

Answer 11

inadequate GI absorption (VitD deficiency), respiratory alkalosis, renal loss

Question 12

Phosphatonins?

Answer 12

FGF23 from bone acts to decrease serum phosphate by increasing renal trnasporters

Question 13

Inhibition of FGF23?

Answer 13

PHEX