Flashcards in Calcium Regulation and Pharmacology Deck (66):
What is calcium?
- major EXTRACELLULAR divalent cation (Ca2+)
- 45% ionized Ca2+ exerts physiologic effects
Where is 99% of calcium stored?
- in BONE
How do we get calcium?
- in the diet.
Do men have more calcium than women?
- YES by a little bit.
*** For what is calcium needed?
- neuronal excitability
- neurotransmitter release
- cardiac function (PHASE 2 of cardiac action potential as calcium enters).
- muscle contractions
- membrane integrity
- blood coagulation
Does calcium use a second messenger system?
What does endocrine regulation of extracellular calcium affect?
- entry at the intestines
- secretion/reabsorption at the kidney
- storage/release (bone absorption/release of Ca2+)
What regulates calcium absorption/excretion?
- kidneys and bones
What are osteoCLASTS?
- break down (reabsorb) bone to INCREASE serum calcium
What are osteoBLASTS?
- build up bone thus DECREASING serum calcium
How is calcium absorbed?
- ACTIVE vit. D-dependent transport in PROXIMAL DUODENUM.
- FACILITATED DIFFUSION in small intestines
- efficiency is inversely related to Ca2+ intake.
Does calcium intestinal absorption increase or decrease with age?
Is vitamin D a fat or water-soluble vitamin?
*remember A, D, E, and K are fat soluble.
What happens to the QT with HYPOcalcemia?
- WIDENS the QT
What happens to the QT with HYPERcalcemia?
- NARROWS the QT
What depresses intestinal calcium transport?
- phenytoin (used for seizures)
What do disease states do to calcium?
- lead to fecal loss of calcium
What regulates urinary excretion of Ca2+?
- PARATHYROID HORMONE (PTH)
*urinary calcium loss is influenced by filtered Na2+ and presence of non-reabsorbed anions.
Can lactation and sweat affect loss of calcium?
Can some diuretics increase urinary loss of Ca2+?
- YES, furosimide
*thiazides will reabsorb calcium!
How often is your entire bone mass modified?
every 6 months via osteoclasts and osteoblasts
What regulates blood calcium levels?
- PARATHYROID hormone by regulating osteoclasts and osteoblasts.
What factors influence bone remodeling?
INCREASE in the activation of remodeling units:
- hypervitaminosis D
What is the etiology of impaired osteoBLASTIC function?
- high dose CORTICOSTEROIDS
- high dose ETHANOL
What will augment osteoCLASTIC resorptive capacity?
- decreased estrogen
What promotes HYPOcalcemia?
- deprivation of Ca2+ and vitamin D
What stimulates PTH release?
What are the signs of symptoms of HYPOcalcemia?
- increased neuromuscular excitability
- muscle cramps
- tonic-clonic convulsions (GRAND MAL)
If a patient is having a seizure what should you not forget to check?
What are some hypocalcemic states?
- advance renal insufficiency
- excessive use of K+ phosphate in the tx of DKA
- sodium fluoride (large quantities)
- massive transfusions with CITRATED BLOOD.
How do we treat HYPOcalcemia?
- REPLACEMENT (dietary Ca2+ or IV calcium chloride)
- oral supplements often in combination with vitamin D
What can cause HYPERcalcemic states?
- very high ingestion of Ca2+ (rare except in hypothyroidism)
- milk alkali syndrome
- hyperparathyroidism (MOST COMMON)
- systemic malignancy (looks like holes in the bones)
- vitamin D excess
How do we treat HYPERcalcemia?
- increased Ca2+ EXCRETION (loop diuretics)
- sodium phosphate
What substances are involved with calcium regulation?
- phosphate= binds ca2+
- vitamin D
- calcitonin (tones the bones), lowering serum calcium levels
What does phosphate do to calcium?
- causes precipitation, thus lowering calcium
What does PTH do to phosphate?
- increases urinary excretion of phosphate by preventing its reabsorption in the kidney.
What does vitamin D do to phosphate absorption in the DCT?
- increases it
What are some pathologic states of phosphate?
- RICKETS= vitamin D deficiency
- chronic renal failure
What does PTH do to intestinal Ca2+ absorption?
- increases it
What does PTH do to calcium in the bone?
- mobilizes it by activating osteoCLASTS to break down bone.
*aka increases overall bone resorption.
Where is Vitamin D (calcitriol) synthesized?
- in the skin
What stimulates calcitonin?
- hypercalcemia, to lower blood calcium.
What can stimulate calcitonin release?
What does calcitonin do?
- causes direct inhibition of osteoclastic bone resorption, which results in HYPOcalcemia and HYPOphosphatemia.
- lowers calcium and phosphate in the blood
What is Alendronate?
- inhibits osteoclast-mediated bone resorption
What is Raloxifene?
- reduces bone turnover
- decreases LDL levels (no change on HDL)
- no increase in triglycerides
What are the 2 parts of the adrenal glands?
- cortex (outer part)
- medulla (inner part)
What does the adrenal cortex produce?
- minearlocorticoids= aldosterone (N+/K+ balance)
- glucocorticoids= cortisol (raises glucose and suppresses inflammatory response).
- adrenal androgens
What does aldosterone do?
- causes the DCT to reabsorb Na+ and thus water
What are the 3 levels of the adrenal cortex?
- zona GLOMERULOSA= produces ALDOSTERONE
- zona FASCICULATA= produces CORTISOL
- Zona RITICULARIS= DHEA, androstenidione
What does the adrenal medulla?
- EPINEPHRINE= increased chronotropy and inotropy, bronchodilation, increased glucose
- NOREPINEPHRINE= ditto
What is needed for synthesizing adrenal hormones?
What is prednisone?
- glucocorticoid that is 4x as potent as cortisol, used to suppress the inflammatory response.
What is mehtylprednisolone?
- synthetic glucocorticoid that is 5x as potent as cortisol.
What is dexamethasone?
- glucocorticoid that is 30x as potent as cortisol
Do plasma proteins bind adrenocortical hormones?
Where are adrenal hormones metabolized?
What electrolyte problems can we see with low levels of mineralocorticoids?
- sodium chloride wasting and high potassium in the blood.
What can HYPOkalemia lead to?
- muscle weakness
- cardiac conduction issues
What acid base issue can elevated aldosterone cause?
- METABOLIC ALKALOSIS
*remember H+ follows K+
What do glucocorticoids do?
- stimulate GLUCONEOGENESIS in the liver
- decreased glucose utilization by cells
- STEROID INDUCED DM
- reduction of cellular protein
- increased liver and plasma proteins
How does cortisol mitigate stress and inflammation?
- stabilize lysosomes
- decreases eosinophils and lymphocytes
What is Addison's disease?
- hypoadrenalism (mineralocorticoid deficiency)= loss of NaCl and water, hyponatremia, hyperkalemia, mild acidosis, increased RBC concentration, decreased CO, and death.
What will glucocorticoid deficiency lead to?
- low glucose
- muscle weakness
- respiratory difficulties
Do the adrenal glands contribute to precursors of melanin pigmentation?