PHARM 3: Osteoporosis, Calcium Disorders and Parathyroid Disorders Flashcards
Three principal hormones regulate calcium and phosphate homeostasis and their origin?
Parathyroid hormone (PTH) (Chief cells of parathyroid gland)
Active metabolite of vitamin D (1,25-dihydroxy vitamin D) (Calcitriol) made in kidney
Calcitonin (perifollicular cells of the thyroid gland)
________ stimulates the production of the active metabolite of vitamin D (1,25-dihydroxyvitamin D) (calcitriol) in the ________
PTH stimulates the production of the active metabolite of vitamin D (1,25-dihydroxyvitamin D) (calcitriol) in the kidney
___________ stimulates intestinal absorption of phosphate and calcium
Calcitriol (1,25(OH)2D)) stimulates intestinal absorption of phosphate and calcium
_________ and __________ suppress the production of PTH
Calcium and Calcitriol (1,25(OH)2D) suppress production of PTH
__________ promotes bone formation stimulating the differentiation of osteoblasts and ___________ promotes resorption by stimulating the proliferation and differentiation of osteoclasts.
Continuous vs. Pulsaitle Secretion?
Calcitriol (1,25(OH)2D) promotes bone formation stimulating the differentiation of osteoblasts and PTH promotes resorption by stimulating the proliferation and differentiation of osteoclasts.
Continuous PTH = bone resorption
Pulsatile PTH = bone formation
_______________ and ______________ both promote renal retention of calcium
Calcitriol (1,25(OH)2D) and PTH both promote renal retention of calcium
___________ promotes renal phosphate excretion whereas ____________ promotes renal reabsorption of phosphate
PTH promotes renal phosphate excretion whereas Calcitriol (1,25(OH)2D) promotes renal reabsorption of phosphate
Calcitonin MOA?
Released by perifollicular C-cells of the thyroid gland in response to high Ca 2+:
- Binds receptors on osteoclasts to decrease reabsorption of Ca2+
- Increases renal excretion of Ca2+
What is secreted by perifollicular cells of the thyroid gland in response to high Ca 2+?
Calcitonin
What increases calcitonin levels?
High Ca2+
Gastrin
Glucagon
Epinephrine
Calcitonin vs. PTH?
Significance of RANKL?
RANKL binds RANK receptor on Macrophages and promotes differentiation into Osteoclasts
=>INCREASES Bone Reabsorption (Decreases Bone Mass)
Mice Deficient in RANKL Have ‘Stone Bone’ (Osteopetrosis)
Causes of Hypercalcemia?
Hyperparathyroidism
Cancer
Chronic Kidney Disease
Causes of Hypocalcemia?
Hypoparathyroidism
Vitamin D deficiency
Chronic renal failure
Malabsorption
Primary versus Secondary Hyperparathyroidism?
Primary: spontaneous overproduction of PTH)
Secondary: primarily attributable to chronic kidney disease (kidneys fail to activate vitamin D => failure to negative feedback on PTH production)
Symptoms of Hyperparathyroidism?
Painful Bones (increased resorption=> Increased osteoclast activity=> increased risk of osteoporosis )
Renal stones
Abdominal groans
Psychic moans
Therapies for hyperparathyroidism?
Therapies aimed at inhibiting osteoclast activity (overlap with osteoporosis medications)
- Cinacalcet: prevents PTH release from parathyroid by binding to the calcium receptor
- Bisphosphonates: Promotes osteoclast apoptosis and inhibits the cholesterol biosynthetic pathway
- Surgery (95% success rate) but life-long replacement with vitamin D/Calcium will ensue.
Diagnosis of Hyperparathyroidism?
Measuring albumin-adjusted serum calcium
Measuring parathyroid hormone
Osteopenia vs. Osteoporosis?
Osteopenia is 1-2.5 standard deviations below the mean peak bone mass
Osteoporosis is defined as osteopenia that severe enough to cause fracture (at least 2.5 standard deviations below the mean bone mass)
Risk Factors for Osteoporosis?
Hormonal influences –menopause
Steroid hormone use
Also:
Reduced physical activity (weight bearing)
Nutrition (calcium deficiency, vitamin D deficiency)
Genetics (LRP4 mutation)