Term
| Name some functions of calcium. |
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Definition
1. 99% is found in bones and teeth 2. Acts as 2nd messenger in intracellular messenging. 3. Is a cofactor in blood clotting 4. Excitation contraction coupling reactions in muscles 5. Involved in nerve excitability |
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Term
Compare and contrast how calcium and phosphate are distributed throughout the body. |
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Definition
Bone and teeth 99% of body's Ca 86% of body's Phosphorus Extracellular Fluid .1% Ca .08% Phosphorous Intracellular Fluid 1% Ca 14% Phosphorous |
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Term
| What are the inorganic components of bone? |
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Definition
component (% of body's content) 1. Calcium (99%) 2. Phosphate (85%) 3. Carbonate (80%) 4. Magnesium (50%) 5. Sodium (35%) |
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Term
| What is an important function of carbonate? |
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Definition
| It acts as a buffer for pH balance in the blood. |
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Term
| What percent of the body's calcium is found in the blood, name the three components of free calcium and their percentages. |
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Definition
1% of the body's calcium is found in the blood. 40% is Protein Bound -Buffers the blood -As pH rises, more Ca become bound 50% is Free Calcium 10% is Complexed with anions The Free Calcium and complexed calcium (60%) are called FILTERABLE CALCIUM, b/c they pass through the kidneys |
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Term
| What percentage of phosphate is found in the blood/plasma. Of the blood phosphate levels, what percentage is ionized, protein bound, or complexed? |
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Definition
About 15% (extracellular and Intracellular) 84% ionic form 10% protein-bound 6% complexed with ions Most found within cells -phospholipids, DNA/RNA |
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Term
What happens to MOST of the calcium you ingest? What about phophorous? |
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Definition
70% is excreted in the feces Most of the phosphorous is excreted in the urine. |
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Term
| Which nutrient is more readily absorbed by the intestines, calcium or phosphorus? |
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Definition
Phosphorus! Phosphorus is then primarily excreted through the kidneys. Calcium is not well absorbed by the intestines and is mostly excreted in the feces. |
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Term
| What hormones affect bone growth? |
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Definition
Insulin like growth factor (IGF-1) Growth Hormone (GH) Insulin T3/T4 |
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Term
| How many parathyroid glands do people usually have, where are they derived from, and where do they reside? |
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Definition
1. People usually have 4 PT glands (some have 5) 2. Derived from 3rd and 4th Brachial Pouches 3. Reside on the dorsal side of thyroid gland |
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Term
| What are the primary cells of the parathyroid gland that secrete PTH? |
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Definition
Chief Cells secrete parathyroid hormone Oxyphil cells have no known function -noted in hypercalcemia (pathology) |
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Term
What type of hormone is PTH? Describe its synthesis |
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Definition
Parathryroid Hormone is a polypeptide hormone. synthesized as a pre-pro-hormone--> pro-hormone--> active hormone half-life is only a few minutes |
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Term
| What is the primary impetus for the secretion of PTH? |
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Definition
LOW blood calcium* sensed in chief cell PTH acts to raise blood calcium levels *(Romito had this wrong in lecture) |
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Term
During hypercalcemia, what happens on the surface of the chief cell? |
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Definition
A special receptor on the surface of the chief cell senses the excess of calcium in the blood. 1. phopholipase C pathway is activated 2. DAG/IP3 3. Secretion of PTH is decreased or inhibited |
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Term
| What are the direct actions of PTH? |
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Definition
Overall RISE in Blood Calcium Kidneys Reabsorption of Ca2+ Inhibition of phosphorus reabsorption Bone Osteolysis Differentiation of osteoclasts (many more) Increase in Bone Resorption (Ca mobilization) |
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Term
| What is osteocytic osteolysis, and when/why does it occur? |
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Definition
It is an increase in permeability in osteoblasts and osteocytes so calcium is pumped out into the blood. Occurs during hypocalcemia when PTH is high. |
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Term
| What is PTH's effect on kidneys; where on the kidney does this happen? |
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Definition
PTH acts on the distal tubule of the kidney to promote calcium reabsorbtion. PTH binding activates a cAMP pathway which opens up MORE calcium channels Main goal is raising blood calcium! |
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Term
| What is PTH's affect on the proximal tube of the kidney? |
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Definition
Promotes phosphate excretion 1 alpha-hydroxylase converts an inactive form of Vitamin D into the active form 125-vitamin D3. |
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Term
| What is vitamin D derived from and what are the body's primary sources? |
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Definition
Vitamin D is derived from cholesterol 1. 7-dehydrocholesterol is converted to Vitamin D3 in the skin by sunlight. Accounts for 50% 2. The other 50% comes from diet. |
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Term
| Describe the activation of Vitamin D |
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Definition
1. Cholesterol in the diet is converted to 7-dehydrocholesterol 2. This precursor is then converted with the help of sunlight to Vitamin D3. 3. The Vit-D3 is converted to 25-OH-vitamin D3 4. The 25-OH-vitamin D3 is then converted to its active form, 1-25-OH-vitamin D3 by 1-alpha-hydroxylase in the KIDNEYS! 5. Biological Effects |
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Term
What is the main goal of vitamin D on the intestinal wall? |
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Definition
Increase calcium absorption -achieves this by facilitating activity of calcium transporter-1 (epithelial calcium channels) -Activates absorption of calcium AND phosphate (different than PTH in kidney which excretes phosphate and absorbs calcium) |
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Term
What are the physiologic effects of calcitonin? -Where is it secreted from? |
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Definition
Bone inhibits osteoclastic activity Kidneys promotes the excretion of clacium and phosphate Secreted by the parafollicular cells, C-cells, in the thyroid gland. |
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Term
| What is the activated form of Vitamin D and what are its functions on the kidneys, intestine, and bone? |
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Definition
1,25-(OH)2 D3 Kidneys- increases phosphate and calcium reabsorption Intestine- Increases calcium and phosphate absorption Bone- promotes PTH action |
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Term
| What are the signs, symptoms, and causes of hypercalcemia? |
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Definition
Causes Excess production of PTH -Can be an andenoma on the parathyroid -can also be from chronic renal failure Sign/symptoms Stones- Kidney stones Bones- Bone pain (BONE LOSS) Groans- constipation and abdominal cramping Moans- brain nerve impulses are affected (depression) |
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Term
| What are the signs and causes of hypoparathyroidism? |
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Definition
Cause Decreased PTH and decreased active Vitamin D -Means low blood calcium and high phosphate lvls Signs Tetany, convulsions, parethesias Shows CHVOSTEK'S SIGN (Tap CN-7, whole face twitches) Treat with calcium, vit. D, thiazide diuretics |
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Term
| What disease is caused by a vitamin D deficiency? |
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Definition
RICKETS! Bones do not mineralize, legs bow under weight of child In adults it is called osteomalacia -may occur after multiple pregnancies |
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Term
| Describe Paget's Disease. |
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Definition
Also known as Osteitis deformans Disorder of bone remodeling Signs and Symptoms deformity of bones, pain, fracture, arthritis, and compression of nerves. Treatment Treated with bisphophonates and surgery |
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Term
| Describe pseudohypothryroidism. |
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Definition
AKA Albright's Disease Cells are resistant to PTH -Body has high concentration of PTH Causes hypocalcemia and hyperphosphatemia |
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Term
| What is the most common endocrine disease? |
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Definition
Osteoporosis 10 million U.S. cases |
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Term
| What are the types of osteoporosis? |
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Definition
Primary Type 1- post menopausal Type 2- age-related bone/renal function decreasing Secondary Type 3- Long term steroid users Other bone and metabolism diseases |
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Term
| What are the risk factors, signs and symptoms, and treatment of osteoporosis? |
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Definition
Risk Factors Diet and Exercise signs and symptoms DOWAGER'S HUMP Treatment bisphosphonates, estrogen, PTH, calcium, exercise |
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