Phys 75: Calciotropic Hormones

Front 1

Describe the signaling that controls the release of PTH from the parathyroid cells

Back 1

When there is increased serum calcium, it binds the calcium receptor at the parathyroid cell. Receptor binding decreases the secretion of PTH. Low PTH means less calcium reabsorption so blood calcium level is decrease. When serum calcium is low, the receptor will not be engaged and PTH secretion will occur.

Front 2

Name 3 ways that PTH works to increase blood calcium

Back 2

1. Activates 1 a hydrolyase in the kidney to increase production of 1,25 (OH2) D which facilitates Ca abs from the intestine 2. Increases bone resporption releasing Ca and PO4 into the blood 3. Increases reabs in the distal tubule

Front 3

describe the activation of vitamin D

Back 3

unregulated 25 hydroxylation at the liver, regulated 1 hydroxylation at the kidney-activated by PTH

Front 4

Describe the clincial interpretation of serum vitamin D metabolies (which one tells you what)

Back 4

25OHD is an index of vitamin D stores, it is not altered by changes in 1 hydroxylase (PTH) activity

1,25OHD is an index of renal hydroxyase activity.

Front 5

What is the effect of PTH on phosphate levels

Back 5

PTH decreases reabsorbption of PO4 in the proximal tubule, this is necessary because the bone releases both Ca and  PO4 when reabsorbed, the excess PO4 must be excreted

Front 6

Give 3 possible causes for high serum calcium, how coudl you distinguish

Back 6

1 primary hyperparathyrodism (confirm low PO4 in plasma high in urine, high Ca in urine, high serum 1,25OH2D, low bone density) 2. vitamin D intox 3. PTHrp malgnancy (confirm low PTH)

Front 7

Give 3 possible causes for low serum calcium. Distinguish

Back 7

1. primary hypoparathyrodism ( confirm low 1,25 OHD, low PTH )2. Malabsorption 3. renal failure (for 2 and 3 confirm high PTH)