Endocrine 4-6 Flashcards
Which body systems utilize calcium?
Nervous, muscular and skeletal system (99% found in bone)
What is calcium regulated by?
PTH, calcitonin and active vitamin D
The 1% of calcium circulating in the blood is in what 3 forms?
- Free ionized form 45%
- Bound to proteins 45%
- Complex anions 10%
What is the total serum calcium?
8.5-10.5mg/dL
What is the net effect of parathyroid hormone?
Increase in serum calcium and decrease in serum phosphate
What is calcitriol the active form of?
Vitamin D
What is the function of calcitriol?
Enhances intestinal cells to absorb calcium and phosphate into the serum
What are the net effects of calcitriol?
Increase serum calcium
Increase serum phosphate
Where is calcitriol derived from?
Diet or UV light, required enzymatic steps in liver and kidney to become active vitamin D
PTH is synthesized and secreted by what?
Chief cells of the parathyroid gland
In response to low serum Ca++ bone does what?
Bone: PTH stimulates resorption (osteoclastic) which leads to INCREASE in serum Ca++
In response to low serum Ca+++ kidney does what?
PTH promotes Ca++ resorption and stimulates hydroxylation of 25-hydroxyvitamin D (calcidiol) via an enzyme
In response to high serum Ca+++
PTH decreases its production
Increased serum calcium leads to what?
Decreased PTH
Decreased serum calcium leads to what?
Increased PTH
When PTH stimulates the bone what does it do?
Increases osteoclastic activity and decreases osteoblastic activity
When PTH stimulates GI tract what does it do?
Vitamin D: increased absorption of calcium and phosphate
When PTH stimulates the kidneys what does it do?
Activates 1alpha D hydroxylase, increases reabsorption of calcium and increases phosphate excretion
What effect does calcitonin have on the GI tract?
None
What effect does calcitonin have on the kidney?
Decreases absorption of calcium and phosphate
What effect does calcitonin have on the bone?
Increases osteoblastic activity and decreases osteoclastic activity
Hypocalcemia etiologies from the parathyroid
Thyroidectomy, iodine therapy, autoimmune, infiltrative disease, PTH resistance
Hypocalcemia etiologies from Vitamin D deficiency
CKD: #1 cause, malabsorption syndromes, decrease exposure to sunlight, vitD resistant rickets, hyperphosphatemia, drugs accelerate CP450: Phenytoin
Miscellaneous etiologies for hypocalcemia
Hungry bone syndromes, osteoblastic bone metastases, pancreatitis, multiple transfusion, acute respiratory alkalosis, bisphosphonate OD, alcoholics