Calcitonin/Parathyroid Flashcards
Where is calcitonin synthesized?
Parafollicular cells AKA C-cells of the thyroid gland ***
What is the chemical class of calcitonin?
PPP
What are the primary functions of calcitonin?
Decrease plasma calcium **
Decrease osteoclast cell synthesis **
Decrease 1 hydroxylase enzyme activity
What are the secondary functions of calcitonin?
Decrease digestion, PAIN ***, plasma phosphorus, and plasma sodium
If calcitonin’s ability to decrease pain is a secondary function, what possesses the primary function of decreasing pain?
Endorphins
Calcitonin controls the secretion and concentration of what substance?
Plasma calcium concentration
Where can some calcitonin be secreted besides the C cells of the thyroid?
Thymus and parathyroid
What is the effect of calcitonin on bone reabsorption? ***
Inhibition
What does calcitonin do in the body?
Lowers calcium and phosphate in plasma ***
Calcitonin can be used as treatment for what conditions?
Osteoporosis and Paget’s disease ***
When is calcitonin used as treatment for osteoporosis?
If patient has adverse reactions to bisphosphonates
How does calcitonin work as treatment for osteoporosis?
Prevents fractures
What happens to bone with osteoporosis?
Bone mass and bone strength decreases
Porous bone
Bone breaks easily
What is Paget’s disease (osteitis)?
Disorder of the normal bone remodeling ***
Bone formed is abnormal, enlarged, and weak
Does the bone remodeling process occur faster or slower in patients with Paget’s disease?
Faster (therefore weak bone is formed)
Paget’s disease is more common among what age group?
Over 50
What are the symptoms of Paget’s disease?
Pain in bone/spine, fractures, bowed legs, cauda equina syndrome, enlarged skull (possible hearing problems)
What are treatment options for Paget’s disease?
Bisphosphonates or calcitonin (if side effects seen with bisphosphonates)
Parathormone (parathyroid hormone) essentially is the opposite of what other hormone?
Calcitonin
Where is parathyroid hormone synthesized? *
Dark chief cells of the parathyroid gland *
What chemical class is PTH?
PPP
What does parathyroid hormone do?
Maintains calcium and phosphorus in plasma ***
What condition arises from a deficiency in PTH?
Hypocalcaemia (decreased calcium in blood)
What are the primary functions of parathyroid hormone? *
Stimulate growth *
Increase 100% vitamin D synthesis **
Increase plasma calcium *
Decrease plasma phosphorus
What is the means by which parathyroid hormone stimulates growth and increases vitamin D synthesis?
Stimulation of 1-hydroxlase enzyme synthesis
What is the means by which PTH increases plasma calcium? *
Increases renal reabsorption of calcium
What is the most powerful hormone to increase plasma calcium? *
Parathyroid hormone (PTH) ***
Does PTH stimulate osteoblast or osteoclast activity?
Osteoclast
How does PTH decrease plasma phosphorus?
Decreases renal reabsorption of phosphorus
What is the most powerful hormone to decrease phosphorus in plasma?
PTH
PTH controls the secretion of what substance?
Plasma calcium
What are the secondary functions of PTH? *
Big 4: increase metabolism, plasma glucose, BP, and immune response **
Also decreases plasma bicarbonate
What can cause hypercalcemia?
Increase in hormones that increase plasma calcium
Decrease in hormones that decrease plasma calcium
Excessive sunlight, malignancies, hypervitaminosis
Liver/kidney disorders
Where is vitamin D synthesized?
Liver * (25-(OH) D3) and kidney (all active forms) *
What is the chemical class of vitamin D?
Seco-steroid
What is the precursor molecule of vitamin D that we obtain from our diet and sunlight?
7-dehydrocholesterol aka vitamin D3 aka cholecalciferol
What kind of vitamin D do we obtain from supplements?
Vitamin D2
What does the vitamin D become that is obtained from sunlight and diet when it is hydroxylated in the liver?
25-hydroxycholecalciferol ***(aka calcifediol)
What is the final form of vitamin D seen after it passes through the kidneys?
1,25-dihydroxycholecalciferol (aka calcitriol or 1,25(OH)2D3) ***
The activity of what substance leads to tight regulation of vitamin D by the kidneys?
1-alpha-hydroxylase
What is the major controller of 1-alpha-hydroxylase? **
Parathyroid hormone **
What are the primary functions of vitamin D? **
Increase linear height **
Increase plasma calcium **
What are the means by which vitamin D increases linear height?
Stimulation of osteoblast cell activity
Increase intestinal absorption of calcium
What are the means by which vitamin D increases plasma calcium?
Stimulation of osteoclast cell activity
Increase intestinal absorption of calcium
Increase renal reabsorption of calcium
What is the secondary function of vitamin D? *
Stimulate integumentary system (skin and hair) **
Stimulates immune resonse
Increases oxygen transport and plasma phosphorus
What condition results from a deficiency in thyroxine and vitamin D?
Alopecia (hair loss)
What controls the secretion of vitamin D?
Plasma calcium *
Sunlight *
Hormones like PTH, glucagon, cortisol
What hormone is most powerful in decreasing the secretion of vitamin D?
Glucagon
What situations can cause vitamin D deficiency?
Sun shunning *
Strict vegetarian diet *
What are foods that are good sources of vitamin D?
Fish liver oils, egg yolks, some fortified dairy products, fortified grain
What is a major symptom of vitamin D deficiency?
Cognitive impairment *
What conditions can result from vitamin D deficiency?
Rickets, severe asthma in children *, some cancers *, increased risk of cardiovascular disease *
What is the blood test used to determine vitamin D deficiency? *
25-hydroxyvitamin D blood test
What is the normal vitamin D range on a blood test?
20-50 nanograms/milliliter
What level is considered deficient in vitamin D on a blood test?
12 ng/ml **
What is the treatment for vitamin D deficiency?
Short sunlight exposure
Foods rich in vitamin D
Vitamin D supplements if needed (up to 4000 IUs)
