Hormones in calcium metabolism Flashcards Preview

Year 2 Endocrine > Hormones in calcium metabolism > Flashcards

Flashcards in Hormones in calcium metabolism Deck (25):
1

how is PTH synthesized? where?

as prepro-PTH in ribosomes

2

regulation of PTH synthesis and release

- calcium binds to calcium sensing receptor
- PLC-DAG-PKC-PLA2-arachadonic acid-luekotrienes
- leukotrienes inhibit PTH

3

how is PTH synthesis related to calcium?

a relaxed calcium sensor receptor leads to PTH synthesis and secretion

4

where are calcium sensor receptors located?

- parathyroid chief cells
- thyroidal C cells
- kidney tubules

5

via which two pathways is PTH action mediated?

adenylate cyclase pathway
PLC pathway

6

what are the PTH target organs?

kidney
bone

7

how does PTH affect the kidney?

stimulates calcium reabsorption by the kidney (stimulates insertion and opening of calcium channels)

8

how does vitamin D affect the kidney?

stimulates calcium reabsorption by the kidney (activates calcium ATPase and controls calbindin)

9

what is the role of PTH in bone remodeling?

- PTH stimulates production of RANKL
- osteoclast precursors bind to RANK
- inhibits osteoprotegerin (which normally acts to inhibit the RANK-RANKL interaction)

10

what is the main cause of hypoparathyroidism?

surgical removal of parathyroid glands

11

what are the symptoms of hypoparathyroidism?

- hypocalcemia
- increased plasma phosphate
- tetany

12

ergocaciferol

vitamin D2

13

cholecalciferol

vitamin D3 (circulating hormone - clinical relevance for measurement)

14

which vitamin D is produced by the human body in response to sunlight / diet?

vitamin D3 - cholecalciferol

15

vitamin D synthesis pathway

- cholesterol
- sunlight (UVB) converts 7-dehydrocholesterol to cholecalciferol (D3)
- in the liver D3 is converted to 25-hydroxyvitamin D
- in the kidney 25-hydroxyvitamin D is converted to 1,25-hydroxyvitamin D (calcitriol)

16

calcitriol

1,25-hydroxyvitamin D

17

what is the circulating form of vitamin D?

25-hydroxyvitamin D

18

which part of vitamin D synthesis is calcium involved in?

calcium inhibits hydroxylation of 25-hydroxyvitamin

19

which part of vitamin D synthesis is PTH involved in?

stimulates activity of 1a-hydroxylase (conversion to 1,25-hydroxyvitamin D in kidney)

20

what are the target organs of vitamin D?

intestines
kidney
bone
parathyroid glands

21

what does calcitriol do in the intestines?

- stimulates intestinal calcium absorption
- stimulates renal calcium reabsorption
- stimulates bone remodeling

22

calcitonin is synthesized by what cell type?

C cells of thyroid

23

what are the actions of calcitonin?

- bone: inhibits bone resorption
- kidney: increases urinary calcium excretion

24

how does calcitonin treat osteoporosis?

inhibits osteoclast-mediated bone resorption

25

definition: calcistat

the multi organ systemic network that regulates calcium homeostasis