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64 Cards in this Set
- Front
- Back
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Main purpose of PTH
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maintain normal ionized calcium level
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How does PTH help maintain normal ionized calcium levels?
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1) Increases Ca reabsorption by kidney
2) Stimulates bone resorption leading to Ca release into plasma 3) Stimulates formation of active vitamin D 4) Decreases phosphate reabsorption in kidney |
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What decreases PTH secretion?
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negative fb from calcium
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Mutations in the ______ receptor of parathyroid cells lead to familial hyper or hypocalcemia
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calcium-sensing
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2 major hormones regulate calcium levels
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1,25 OH Vit D
PTH |
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1,25 OH Vit D: Effects on calcium metabolism
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<b>Increases Ca and phosphorous absorption in GI tract.</b>
At high levels, stimulates bone resorption by stimulating osteoclast differentiation. |
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What is the main regulator of 1-hydroxylation of Vitamin D?
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PTH
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Where does the conversion of 25 OH Vit D --> 1,25 OH Vit D (1 hydroxylation) occur?
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kidney
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Those who are volume (depleted, overloaded) will have increased reabsorption of sodium and calcium
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Depleted
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Majority of Ca reabsorption occurs in the
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proximal tubule (linked with Na reabsorption)
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Where is the PTH dependent excretion of calcium?
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distal tubule
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If PTH levels are increased, distal tubule calcium reabsorption (increases, decreases)
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increases
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Loop diuretics (increase, inhibit) Calcium reabsorption while thiazide diuretics (increase, inhibit).
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Inhibit; Increase
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Which diuretic class is iused in someone with kidney stones?
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thiazide
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Effect of Hypercalcemia on Renal Water Excretion
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Causes diuresis (nephrogenic DI)
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What is the clinical presentation of hypercalcemia?
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"Stones, bones, abdominal groans, and psychic moans"
Severity dept on degree of hypercalcemia. CNS: lethargy, depression, etc Neuromuscular: weakness Cardiovascular: hypertension, arrhythmia Renal: polyuria, hypercalciurina, stones GI: constipation, N/V MSK: pain Bone: osteoporosis, fractures |
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Differential Diagnosis of Hypercalcemia: First step
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Distinguish between <b>excess PTH</b> and <b> other causes of hypercalcemia</b>.
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Differential Diagnosis of Hypercalcemia: Causes of high PTH
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Primary hyperparathyroidism
Familial hypocalcuric hypercalcemia |
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Most common etiology of high PTH resulting in hypercalcemia?
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Primary hyperparathyroidism
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What is usually cause of primary hyperparathyroidism?
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Adenoma (usually 1 of 4)
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4 parathyroid gland hyperplasia is more likely to occur in (MEN, primary hyperparathyroidism)
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MEN.
Prim hyperpara is more likely to just be 1 of the 4 |
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Primary hyperparathyroidism:
Will see (increased, decreased) Ca and (increased, decreased) phosphate on labs |
Increased; Decreased
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How to distinguish between
Primary hyperparathyroidism Familial hypocalcuric hypercalcemia (FHH) |
In FHH, urinary calcium will be low.
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Differential Diagnosis of Hypercalcemia: PTH Indept
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1) Hypercalcemia of malignancy: Most common (Humoral vs associated with solid tumors)
2) Vitamin D toxicity 3) Granulomatous disease 4) Meds 5) Other endocrine causes |
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Most common cause in hospitalized pts
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hypercalcemia of malignancy
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Why does granulomatous disease cause hypercalcemia?
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Increased formation of 1,25dihydroxyvitaminD within granulomas.
Granulomas have 1-hydroxylase activity, causing increased levels of 1,25OH Vit D |
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Pathophys of immobilization causing hypercalcemia
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Prolonged bedrest results in increased osteoclastic resorption and decreased bone formation
Occurs in context of decreased renal function |
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Elevated PTH with elevated urinary excretion of calcium: what disorder?
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Primary hyperparathyroidism
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Elevated PTH with low urinary excretion of calcium: what disorder?
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familial hypocalciuric hypercalcemia (FHH)
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Clues to diagnosing Vit D poisoning
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Hypercalcemia with low PTH.
Will also see elevated phosphorous |
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Suppressed PTH with normal levels of 25 and 1,25 Vit D: what disorders are possible?
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Hypercalcemia of malignancy, Endocrinopathies
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Acute treatment for any etiology
of hypercalcemia |
Hydration with normal saline : increases hydration and results in increased calcium excretion.
Add loop diuretic AFTER volume repletion. |
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Primary hyperparathyroidism that is symptomatic: Treatment
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Surgery for all symptomatic patients
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Primary hyperparathyroidism that is asymptomatic: Treatment
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bisphosphonates
calcium-sensing receptor agonist (cinacalcet) - binds to Ca sensing receptors and decreases PTH secretion |
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What is cinacalcet?
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calcium-sensing receptor agonist - binds to calcium sensing receptors and decreases PTH secretion
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Pamidronate or zoledronic acid: what are they?
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bisphosphonates
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bisphosphonates: MOA
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Inhibits osteoclastic bone resorption
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Tx of granulomatous diseases (Eg sarcoidosis) that cause hypercalcemia due to increasing Vit D
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steroids
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Total Calcium measured in blood
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Bound Calcium + Ionized = Total Calcium measured in blood
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Clinical symptoms of hypocalcemia
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Impaired NMJ signaling - manifestations
Calcium precipitation |
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3 major questions to approaching hypocalcemia
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1) Is ionized hypocalcemia present? (gets at difference between low albumin)
2) If there PTH deficiency or abnormal PTH action? 3) If no, is there abnormal vitamin D action? |
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If calcium is low and PT glands are normal, PTH should be _______
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increased
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In PTH deficiency vs. Vitamin D deficiency, how will phosphate differ?
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PTH deficiency: phosphate will be high (PTH increases phosphate excretion)
Vit D deficiency : Phosphate will be Low |
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How is ionized calcium affected by pH?
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Alkalosis: Lowers ionized calcium
Acidosis: increases ionized calcium |
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Symptoms of hyperventilation are due to what?
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transient decrease in ionized calcium ---> hypocalcemia
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Signs of hypocalcemia
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Chvostek's sign (Face) and Trusseau's sign (arm)
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Lab findings in hypoparathyroidism
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Decreased calcium
Increased phosphate Normal urinary cAMP response to PTH infusion Increased renal calcium clearance Decreased intestinal calcium absorption |
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Hypoparathyroidism: Tx
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1) Vitamin D: must use physiologic replacement with active vitamin D metabolites or high doses of ergocalciferol
2) Calcium supplements |
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Why is pseudohypoparathyroidism thus named?
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It looks like hyperparathyroidism (Low Ca, high Phosphate) but it isn't.
PTH is actually increased. It is actually <b>PTH Resistance </b>. |
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What will the urinary cAMP response be to PTH infusion in pseudohypoparathyroidism?
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deficient
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Pseudo-pseudo hypoparathyroidism: what is it?
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same genetic defect (PTH resistance) as pseudohypopara, but NO hypocalcemia
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What is the abnormality that causes pseudo hypoparathyroidism?
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Gs alpha abnormality
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Treatment of PseudoHypoparathyroidism
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Same as Hypoparathyroidism: Vit D, Ca supplements
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What is familial benign hypocalcemia?
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asymptomatic hypocalcemia with normal PTH
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What is treatment for familial benign hypocalcemia?
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NONE. Treatment to normalize Ca causes renal insufficiency.
Recognize and do not treat |
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What will cause abnormal 25-hydroxylation of Vitamin D?
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SEVERE liver disease, microsomal enzyme inducers (phenobarb, alcohol)
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Abnormal 1-hydroxylase: Causes
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Renal disease (common)
1- hydroxylase deficiency |
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Abnormal vitamin D action: causes
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Abnormal vitamin D receptor
Glucocorticoid treatment Aging? |
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Clinical Manifestations-Classic D Deficiency
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1) Hypocalcemia
2) Increased PTH 3) Decreased phosphorous 4) Possibly osteomalacia |
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Vit D deficiency: tx
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supplementation of Ca and Vit D
(Tx guidelines are similar to those of hypoparathyroidism) |
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refers to the excessive secretion of parathyroid hormone (PTH) by the parathyroid glands in response to hypocalcemia
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Secondary hyperparathyroidism
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Secondary hyperparathyroidism is especially common in what patients?
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those with renal failure
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25 OH vitamin D target :
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> 30 ng/ml
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If serum calcium is low and parathyroid glands are normal, there shuld be an ______ in PTH and its physiologic effects
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Increase
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