(parathyroid-patho) Fundamentals of Investigation Of Bone Diseases Flashcards
Most abundant mineral in the body?
Calcium
99% of Ca is found in?
W the other 1%?
99% of Ca is found in bone
1% found in blood
The concentration of calcium, phosphorous & magnesium in the plasma depends on:
- Net effect of bone mineral deposition & resorption
- Intestinal absorption
- Renal excretion
What are the hormones that regulate Ca?
- PTH
- Calcitriol (active form of vitamin D)
- Calcitonin (minor role)
PTH is secreted by?
Chief cells in the Parathyroid gland
What is the principal regulator of the Ca concentration?
PTH
PTH secretion is stimulated when there is ___________________________ levels.
PTH secretion is stimulated when there is decrease in serum ionized calcium levels.
What are the actions of PTH?
• Stimulating calcium release from bone (primary target) by increasing osteoclast bone resorption
• Promoting renal tubular calcium reabsorption
• Increasing renal tubular phosphate excretion
• Enhancing renal conversion of inactive Vit D to its Active form
Where is vit D3 activated?
In the liver and kidneys
Explain the process of vit D metabolism (+ mention where it takes place)
- Cholecalciferol (Vitamin D3) is derived from 7-dehydrocholesterol in the skin by sunlight or supplied in the diet
In liver:
2. Cholecalciferol is converted to 25-hydroxycholecalciferol (25-HCC) by the enzyme 25 hydroxylase
In kidneys:
3. The 1 α hydroxylase enzyme converts 25 hydroxycholecalciferol to 1,25-dihydroxycholecalciferol (1, 25 DHCC or Calcitriol) which is the biologically active form of vitamin D
What is the main storage form of Vit D in the body and its predominant form in the blood.
25-hydroxycholecalciferol
Deficiency of
Deficiency of Calcitriol leads to ?
Defective bone mineralization
Which hormone is the ONLY hypocalcemic hormone?
Calcitonin
Calcitonin hormone is secreted by? And why?
The parafollicular/“C” cells of the thyroid in response to hypercalcemia
