Endocrinology 16 Flashcards
What is PTH regulated by?
The amount of calcium in the blood
How does low calcium affect PTH?
It increases the amount of PTH
How does high calcium affect PTH?
There is a decrease in the output of PTH
What do calcium sensors on the chief cells of the parathyroid do?
They bind to calcium and cause changes inside the cell which in turn lead to changes in PTH
What happens when calcium levels outside chief cells goes up?
It decreases the output of PTH from the cell which brings down the blood calcium level
What happens when calcium levels outside chief cells goes down?
Increased PTH will increase blood calcium. This occurs by increasing cyclic AMP (cAMP) less Gq IP3 and Ca2+ in the cell which overall will increase PTH
What are the two sources of vitamin D?
•Diet
What class of hormones does vitamin D belong to?
The steroid hormones
What is the starting substance for vitamin D?
7-dehydrocholesterol in the skin
What happens to 7-dehydrocholesterol in the skin in the presence of sunlight?
It is converted to vitamin D3
What happens to vitamin D3 in the liver?
It is converted to 25-OH Cholecalciferol
What is the major form in which vitamin D is stored?
25-OH Cholecalciferol
What produces the active form of vitamin D?
The kidneys
How do the kidneys produce the active form of vitamin D?
In the presence of 1-alpha hydroxylase it converts 23-OH cholecalciferol to Active vitamin D
What is 1alpha hydroxylase stimulated by?
PTH
