Parathyroid Hormone and Calcitonin

Question 1

what is the importance of correct calcium levels within the body?

Answer 1

it is important for

• bone and tooth formation
• cell division and growth
• neuronal activity
• skeletal and smooth muscle activity
• cardiac activity and blood coagulation (clotting)
• secretory activity of glands

Question 2

what is calcium homeostasis/

Answer 2

governed by a balance of calcium ion absorption, excretion and storage. Regulation of this is by two key hormones calcitionin and parathyroid.

Question 3

what are osteoblast?

Answer 3

type of bone cell that synthesis bone tissue

Question 4

what is an osteoclast?

Answer 4

type of cell that resrobs bone tissue, this is critcial in the maintainece of long bones

Question 5

what diseases affect calcium ion homeostasis?

Answer 5

• primary hyperparathyroidism
• secondary hyperparathyroidism
• osteoporosis
• rickets
• calcium stones
• receptor mutations

Question 6

what is calcitionin?

Answer 6

thryocalcitionin.
small protein hormones (32aa) produced primarily by parafollicular ~C cells
half life is around 5 minutes.

Question 7

what is the main function of calcitionin?

Answer 7

reduce blood calcium ion concentration. it also opposes the effects of parathyroid hormone which is made by cells in the parathyroid cell

Question 8

how many parathyroid cells are in most people?

Answer 8

4 -located on the posterior surface of the thyroid gland

Question 9

what are the 2 cell types of parathyroid gland?

Answer 9

1. Chief cells

2. oxyphil cells

Question 10

what is the fucntion of chief cells/

Answer 10

produce parathyroid hormone, small helical protein of 84 aa.
half lifwe under 20 mins
increase blood calcium ion conc when it gets too low – this is detected by g-coupled protein receptors coupled to a calcium ion sensing receptor (CaSR)

Question 11

how does parathyroid hormone work (PTH)?

Answer 11

it raises blood calcium ion concentration by

• indirecetly stimulating osteoclast to release more calcium ions from the bone
• increasing renal calcium reabsorption, reducing amount excreted
• increasing production of vitamin D, which stimulates the uptake of calcium ions from the intestine

Question 12

how do they regulate negatve feedback of calcium/

Answer 12

increase in blood calcium ion level decreases with PTH secretion
the increase in blood calcium ion level increases bone formation

Question 13

how does calcitionin work?

Answer 13

reduces osteoclast activity to reduce bone resorption and allows rapdi bone deposition by osteoblasts. opposite effect to PTH