PARATHYROID ENDOCRINOLOGY & CALCIUM REGULATION Flashcards
____ Homeostasis
Essential for:
Bones/teeth
All cells
Nerve/muscle function
Blood clotting
3 hormones responsible:
Parathyroid hormone (PTH)
Calcitonin
Vitamin d
Calcium
Total body calcium = ___ kg
1
Calcium regulation ;
_________ Ca in ECF by:
-exchange between bone and ECF ——>min to min
-Renal excretion regulation
__________Ca by:
-GI absorption of Ca —————> long term regulation
- renal excretion
Free ionized ca
Total body ca
Chief cells have a ____ ion sensing receptor
Calcium
____ is a peptide hormone
Control by a neg feedback loop:
-synthesis&secretion stimulated by low plasma ionized Ca2+
-raises free ionized Ca2+ in ECF
- Activity is essential for life
-acts on bone, kidneys, and via Vit.D -GI tract
Parathyroid hormone
Osteoblasts, osteoclasts, or osteocytes ?
____ create new bone by secreting organic matrix - osteoid- and then mineralizing it with calcium phosphate crystals
Osteoblasts
Osteoblasts, osteoclasts, or osteocytes ?
____ arise from entombed osteoblasts, involved in calcium regulation but do not create bone
Osteocytes
Osteoblasts, osteoclasts, or osteocytes ?
_____ dissolve bone by solubility green the crystals
Osteoclasts
_____ create bone throughout life = bone deposition
____dissolve bone = bone resorption
Osteoblasts
osteoclasts
PTH stimulates :
Movement of ionized ___ from bone to fluid to ECF (fast response time)
Ca2+
PTH stimulates :
Bone dissolving activity of ____ (slower response time)
Osteoclasts
PTH increases renal reabsorption of ___
And increases excretion of ___
PTH induces activation of _____
Phosphate
Calcium
Vit d ?
Calcium
Phosphate
Vit d
_____
effects on bone remodelling opposite to PTH :
A peptide hormone
Decreases movement of ionized calcium from bond fluid to ECF
Inhibits activity of osteoclasts; therefore decreases bone resorption
Increases renal calcium excretion
Calcitonin
_______
-Derived from inactive form produced in skin by action of sunlight, present in some foods
-biologically inactive precursor os called 7-dehydrocholesterol
-is a steroid hormone
Vit d
Vit d is activated by addition of 2 ___ groups
1st in liver —> 25-OH Vit D
2nd in kidneys —> 1,25(OH)2 VitD3
Hydroxyl
______ hydroxylation enzyme is stimulated by :
-PTH
-low plasma ionized calcium
- low plasma ionized phosphate
-prolactin (during lactation)
Kidney
When plasma ionized ____ is high , renal hydroxylation produces an inactive form : 24, 25(OH)2 VITD3
CALCIUM
Effects of activated ______:
- increases total body calcium by increasing GI absorption of calcium
-dose dependent response
-slow, long lasting response
-adjusts Ca2+ intake from diet to match needs is changes in ratio of active/inactive Vit D
VIT D 3
Effects of activated Vit D3 :
- increases __ ionized calcium by enhancing response of bone to PTH
ECF
Hyperparathyroidism
Hypoparathyroidism
Vitamin d deficiency
Osteoporosis
Are problems of ___ homeostasis
Calcium
_______ is a rare condition usually caused by autoimmune disease or physical damage to these glands = low secretion of PTH
Hypoparathyroidism
Paraesthesia
Tetany
Pins and needles sensation = ___
Muscle spasms =____
Paraesthesia
Tetany
Hyperparathyroidism can cause _____ results from high PTH
Hypercalcemia
______ causes high PTH production due to chronic renal disease or vit d deficiency
Hypocalcemia
High ___ with elevated ___ causes:
Depressed muscle/nerve excitability
Increased risk of fractures
Risk of kidney stones
PTH
Ca2+
High PTH causes Bone demineralization in :
Children = ____
Adults = ___
Rickets
Osteomalacia
Rickets
Osteomalacia
Hyperparathyroidism with ____ deficiency :
Impairs GI absorption of calcium
Results in high PTH causing bone demineralization
VIT D
_______ pigmentation affects vit d production
Skin
______- brittle bones :
-condition in which bone resorption is Greater then bone formation
-reduced osteoblast activity=increased osteoclasts activity
-plasma calcium, phosphate, PTH and Vit D evens are usually normal
=reduction of bone mass
Osteoporosis
