Flashcards in LMP301 Lecture 11: Calcium, Vit D, Parathyroid Deck (90)
Where is calcium excreted?
- intestines (poop)
Which hormones regulate calcium homeostatsis?
- parathyroid hormone
- 1,25 (OH)2 vit D
What stimulates PTH release?
effect of PTH on bone
reabsorption (break down)
effect of PTH on kidney
- Ca++ reabsorption
- P secretion
- incr. 1-OH'ase
- incr. 1,25 (OH)2 vit D
Where does PTH act on?
How do we get to the active form of 1,25 (OH)2 vit D?
1. pro-vitamin D --(UV)--> vit D
2. vit D --(25-OH'ase)--> 25-(OH)D3
3. 25-(OH)D3 --(1a-OH'ase)--> 1,25-(OH)2D3
Where can 25-OH'ase be found?
where can 1a-OH'ase be found?
many tissues, including kidneys, pancreas, colon, prostate, breasts...
The active 1,25 (OH)2 vit D can be converted into the inactive...
25 OH vit D can be converted into ____ by ____ (not the reaction to make 1,25-(OH)2D3)
Sources of vit D3
- sunlight on skin
function of 1,25-(OH)2D3 at pancreas, colon, prostate, breasts...
regulate cell growth (prevent cancer)
Prevent autoimmune diseases
function of 1,25-(OH)2D3 at kidneys
prevent autoimmune diseases
maintain calcium homoeostasis (muscle & bone health)
Where does 1,25-(OH)2D3 act on?
- parathyroid gland
effect of 1,25-(OH)2D3 on intestines
- increase Ca absorption
- incr P absorption
Overall effect of 1,25-(OH)2D3
raise blood Ca++ levels
effect of 1,25-(OH)2D3 on bone
effect of 1,25-(OH)2D3 on parathyroid gland
Feedback of 1,25-(OH)2D3
- inhibit its own synthesis
- promotes its own breakdown
1,25-(OH)2D3 is bound to ___ when in circulation
vit D binding protein
receptor for 1,25-(OH)2D3
nuclear vit D receptor
calcitonin is secreted by...
parafollicular / C cells of thyroid gland
Secretion of calcitonin is stimulated by...
- high Ca
- GI hormones
Effect of calcitonin
- lower serum CA
- lower serum P
- stops bone reabsorption
Calcitonin is used as treatment for which bone diseases?
- post-menopausal osteoporosis
- Paget's disease
Calcitonin is a tumour marker for...
medullary thyroid carcinoma (tumor of the C cells in thyroid gland)
Tetany is a symptom of...
flexed wrist & ankle joint, muscle twitching, cramps