Endocrine: Lecture 11: Parathyroid hormone (PTH)
What are the functions of Parathyroid hormone?
1. It stimulates osteoclasts to digest bone matrix and release Ca2+ to blood. 2. Enhances reabsorption of Ca2+ and secretion of phosphate by kidneys 3. Promotes activation of vitamin D (by kidneys), 4. Increases absorption of calcium by intestinal mucosa
PTH fill in. Hormone: Stimulus: Endocrine gland that produces it: Target(s): Response(s):
Hormone: Parathyroid hormone, PTH Stimulus: low blood calcium Endocrine gland that produces it: parathyroid cells in the parathyroid glands Target(s): osteoclasts (bones), kidney, small intestine Response(s):stimulates osteoclasts activity in bone, reabsorbs calcium in kidney tubules, activated vitamin D in kidneys so the small intestine can absorb calcium out of the food we eat
What is a proliferative tumor?
It causes parathyroid cells to overgrow and develop tumors; the negative feedback regulation is lost, which causes excessive PTH to be made constantly.
What is PTH? Which type of cells secrete PTH?
It helps maintain proper blood calcium levels; it is secreted/made by the parathyroid cells in the Parathyroid gland (the tiny glands embedded on the dorsal side of the thyroid gland)
When is PTH secreted?
When calcium (Ca2+) levels are low.
What causes Hyperparathyroidism?
a proliferative tumor
What are kidney stones (caused by an underactive parathyroid gland)?
calcium can form crystals that get lodged in the ureters = kidney stones
- bones soften and deform (because PTH causes osteoclasts to be stimulated, so they are constantly eating away your bone matrix) - elevated Ca2+ levels depresses nervous system and contributes to formation of kidney stones
effects of Hyperparathyroidism
1. It stimulates osteoclasts to digest bone matrix and release Ca2+ to blood. 2. Enhances reabsorption of Ca2+ and secretion of phosphate by kidneys 3. Promotes activation of vitamin D (by kidneys), 4. Increases absorption of calcium by intestinal mucosa
functions of PTH
What causes Hypoparathyroidism?
gland trauma, removal, or dietary magnesium deficiency
What inhibits the release of PTH?
high blood calcium levels
What is hypocalcemia?
low blood calcium levels
What are some effects of Hyperparathyroidism?
- bones soften and deform (because PTH causes osteoclasts to be stimulated, so they are constantly eating away your bone matrix) - elevated Ca2+ levels depresses nervous system and contributes to formation of kidney stones
It is hard for our bodies to absorb calcium. This is why vitamin D is put in milk, because it helps us absorb calcium better. So when PTH is released, it activated vitamin D by the kidneys. What does this lead to?
Calcium absorption from the food/milk in our small intestine
Hydroxyapatite?
Calcium and Phosphate; it is released when the osteoclasts eat up the bone matrix
How is vitamin D made? Where is the active form made?
In the skin, UV light triggers vitamin D production (but this is not the active form); It is made active when the kidneys activate it by triggering more calcium absorption.
Why is calcium important/critical?
It is critical for the muscular and nervous systems
What happens to the phosphate in hydroxyapatite after the calcium is reabsorbed by the kidneys?
It is excreted out of the body by our kidneys through our urine (it is treated as waste)
What are some effects of Hypoparathyroidism?
Muscular system malfunctions (tetany, respiratory paralysis, and death)
When PTH stimulates the osteoclasts, what happens?
Osteoclast activity in the bone causes hydroxyapatite to be released in the blood.
Which hormone is the most important in calcium (Ca2+) homeostasis?
PTH
What are the parathyroid glands?
They are little glands embedded on the dorsal side of the thyroid gland; there are usually 4 to 8.
What is tetany?
muscles stay contracted
What are the other type of cells in the parathyroid glands whose function is unknown?
oxyphil cells