Parathyroid Hormone And Vitamin D Flashcards
Where is parathyroid hormone released from?
It is released from the parathyroid gland (behind thyroid, 4 small glands)
When is parathyroid hormone released?
When there is a decreased calcium 2+ plasma conc
What does parathyroid hormone do?
Directly increased Ca2+ reabsorption in kidneys (decreasing excretion)
What other function does parathyroid Hormone have other than for calcium?
It stimulates the formation of the active form of vitamin D
From 25OH to 1,25diOH using enzyme 1-hydroxylase
What is the pathway of vitamin D to become activated?
7 dehydrocholesterol —(UVB)—> cholecalciferol (D3) —(25-hydroxylase)—> 25OHvitD (calcediol) —(1-hydroxylase -positive effect by parathyroid hormone) —> 1,25 diOHvitD (calcetriol)
25 - liver
1,25 - kidneys
What endocrine substance is released by the kidney?
Erythropoietin
Where is erythropoietin produced?
In the peritubular cells of the interstitial space of the renal cortex
What does erythropoietin stimulate?
Bone marrow maturation of RBC (erythrocytes)
EPO increased/decreases in response to?
Increase- anaemia, altitude, cardiopulmonary disorders
Decrease- polcythaemia (abnormally high haemoglobin in blood), Renal failure
What is the process of vitamin D activation?
Calcediol (liver) —> calcetriol (kidney)
What 4 parts of the body does vitamin D activation affect?
Intestines
Bone
Kidney
Parathyroid
How does vit D activation affect intestines?
Increased PO4 absorption
Increased Ca2+ absorption
How does vit D activation affect bone?
Increased resorption
How does vit D activation affect kidneys?
Increased Ca2+ and PO4 reabsorption
How does vit D activation affect parathyroid?
Decrease parathyroid hormone
