Chapter 16 - Calcitonin and PTH
Four to eight tiny glands embedded in posterior aspect of thyroid (Hence the name parathyroid)
What are the parathyroid glands and where are they located?
Oxyphil cells and parathyroid cells secrete parathyroid hormone
What do the cells of the parathyroid gland do?
Stimulates Ca2+ uptake and incorporation into bone matrix
What does Ca2+ stimulate?
Enhances reabsorption of Ca2+ and secretion of phosphate by kidneys
What does the PTH enhance?
Increases absorption by vitamin D going into the GI tract (intestinal mucosa)
What does the PTH increase absorption of Ca2+ by?
Increases absorption of Ca2+
What does the PTH increase?
Promotes activation of vitamin D (by kidneys)
What does the PTH promote?
Bones soften and deform
What happens to the bones in hyperparathyroidism?
Parathyroid hormone (PTH)
What hormone is calcitonin an antagonist to?
Parathormone
What is another name for the parathyroid gland?
Produced by parafollicular (C) cells
What is calcitonin produced by?
Due to tumor
What is hyperparathyroidism caused by?
Due to gland trauma or removal or dietary magnesium deficiency
What is hypoparathyroidism caused by?
Most important hormone in regulating calcium levels (Ca2+ homeostasis)
What is the function of the parathyroid glands?
Rising Ca2+ in blood inhibits PTH release
What is the negative feedback control of PTH?
Elevated Ca2+ depresses nervous system and contributes to formation of kidney stones
What is the result of elevated Ca2+ levels in hyperparathyroidism?
Hyperparathyroidism
What is the result of hyper secretion of PTH? (high levels of Ca2+)
Hypoparathyroidism
What is the result of hypo secretion of PTH? (low levels of Ca2+)
results in tetany (muscle spasms), respiratory paralysis (muscles contract and stay contracted - can't breathe), and death
What is the result of hypoparathyroidism?
No known physiological role in humans
What is the role of calcitonin?
Stimulates osteoclasts to digest bone matrix and release Ca2+ to blood (antagonist to calcitonin)
What is the stimulating function of PTH?
Must regulate Ca2+ levels very closely
What must people do who have a homeostatic imbalance of the PTH?
Contain oxyphil cells (function unknown) and parathyroid cells
What type of cells do the parathyroid glands contain?
Antagonistic
What type of hormone is calcitonin? (permissive, synergistic, antagonistic)
Humoral stimuli - interacting directly with the blood
What type of stimuli stimulates the PTH?
Takes Ca2+ from blood to bone
Where does the Ca2+ come from when it is released into bone matrix?
Forces calcium back in bone to make bone stronger
Why would calcitonin be good to treat osteoporosis?
Inhibits osteoclast (breakdown bone) activity and release of Ca2+ from bone matrix
At higher than normal doses, what does Ca2+ inhibit?
Osteoporosis
Since calcitonin inhibits osteoclasts from degrading bones, what disease might high levels of calcitonin be used to treat?