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STEP Pathology > deck_5446052 > Flashcards

deck_5446052 Flashcards

1
Q

Notes on calcium balance in the body

A

Humans generally take in 1000mg of Ca daily, 30% of which is absorbed in the duodenum to disperse in the serum. The intestine put out an additional 150 mg/day into the GI to be excreted and the kidneys put out 150 mg/day in urine.

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2
Q

Where are calcium-sensing receptors found?

A

parathyroid, kidney, C cells in the thyroid, and in boneThis is Gs coupled receptor

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3
Q

How do CaSRs work? Drugs to stimulate?

A

high calcium levelsbinds to reduce PTH secretion via internal cascadeDrugs to stimulate: Cinacalcet

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4
Q

How should the workup of a patient with hypercalcemia begin?

A

1) H&E2) Check albumin and total calcium TWICE to reduce risk of lab error3) Check PTH

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5
Q

What conditions associated with hypercalcemia are PTH dependent?

A

-hyper parathyroidism-familial hypocalciuric hypercalcemia (FHH)-Medication-induced (lithum or HCTZ mediated)

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6
Q

What conditions associated with hypercalcemia are PTH independent?

A

-tumor induced (PTHrP or bone metastases)-granulomatous diseases (TB, sarcoidosis, lymphoma) associated with increased VitD-MM-Hyperthyroidism/adrenal failure-ImmobilizationMed-induced (vitD/A toxicity, milk-alkali syndrome)

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7
Q

How is primary hyperparathyroidism defined?

A

high PTH AND high calcium, low phosphate, and increased cAMP in urine

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8
Q

What the main causes of primary hyperparathyroidism?

A

80-85% adenoma15% hyperplasia (MEN1/2A, HPT-Jaw Tumor Syndrome, familial HPT)1% Parathyroid carcinoma

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9
Q

Is sporadic primary hyperparathyroidism more common in men or women?

A

Women

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10
Q

Risk factors for sporadic primary hyperparathyroidism?

A

age, race (AA>W>H), female

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11
Q

What are the symptoms of primary hyperparathyroidism?

A

Stones, abdominal moans (constripation, nausea), psychic groans (depression, memory loss), and bones (osteoporosis/fractures)the MAJORITY are asymptomatic, or have vague symptoms/general unwellness

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12
Q

What things should be included in a primary hyperPTN workup?

A

calcium, albumin (or ionized calcium), PTH, 25-OH vitD,24 hr urine calcium (to differentiate from FHH)Imaging: thyroid US to start, Tc-sestamibi scan, DEXA scan

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13
Q

What is the preferred Tx of primary parathyroidism?

A

parathyroidectomy

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14
Q

What criteria would suggest the need for parathyroidectomy?

A

calcium 1+ mg/dL above UNLage under 50 yoosteoporosisRenal insufficiency

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15
Q

How is primary HPT managed?

A

-adequate hydration-bisphosphonates-maintain vit D range (20-30 ng/mL)

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16
Q

What is an option for patients who can not or do not want surgery and have moderate hypercalcemia?

A

Cinacalcet

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17
Q

What causes familial hypocalciuria hypercalcemia (FHH)?

A

Inactivating mutations in CaSR (100% penetrant) leading to mildly elevated serum Ca and PTH and hypocalciuria.

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18
Q

How does FHH present?

A

mostly asymptomatic

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19
Q

What labs suggest FHH?

A

elevated PTH and calcium and24hr urine calcium less than 50-100 mg/24 hr

20
Q

Tx of FHH?

A

None

21
Q

How does secondary hyperPTH present in labs?

A

Normal calcium with elevated PTH secondary to the parathyroid gland trying to return calcium to a normal range

22
Q

What are the major causes of secondary hyperPTH?

A

hypocalcemiahyperphosphatemiavitD deficiency

23
Q

What kinds of diseases can produce an inability of the GI to absorb calcium from the GI and thus stimulate secondary hyperPTH?

A

stomach or intestine bypass for obesity surgery (gastric stapling/bypass)-celiac or crohn’s disease

24
Q

What causes tertiary hyperPTH?

A

parathyroid glands develop hyperplasia due to chronic low calcium and/or high phosphorus levels after years of seconday hyperPTH.At one point, these glands become autonomous

25
Q

How does hypercalcemia of malignancy present?

A

They will be sick, not with vague symptoms but signs of hypercalcemia (polyuria, dehydration, abdominal and MSK pain) and symptoms of malignancy (weight loss, anemia, etc.)the PTH level will be suppressed!

26
Q

What cancers are most associated with paraneoplastic hypercalcemia?

A

breast, renal, and squamous cell carcinomas

27
Q

What causes hypercalcemia from malignancy?

A

Mostly fromPTH-related protein (PTHrp) binds to the PTH receptor and function similar to PTH to increase cAMPOther causes:-bony metastases can increase calcium levels-humoral factors (cytokines, TNFa) can activate osteoclasts-MM can cause significant bone destruction

28
Q

How do granulomatous diseases cause hypercalcemia?

A

overexpression of 1,25(OH)2D by MACROPHAGES which causes elevated calcium and phosphate but supressed PTH

29
Q

How does hypercalcemia lead to dehydration?

A

calcium inhibits ADH action to express AQP2

30
Q

How is acute hypercalcemia treated?

A

-address volume status (hydrate)-saline diuresis and furosemide after volume status is correctedcalcitonin (only works for 36-48 hrs)Bisphosphonates (panidronate IV works for 2-3 wks or Zoledronic acid IV-works for 1-3 months)glucocorticoids(myelona, granulomatous disease, and vitD toxicity)anddialysis

31
Q

What are the signs of hypocalcemia?

A

agitationhyperreflexiaconvulsionsHTNQT prolongation

32
Q

Causes of hypocalcemia caused by hypoparathyroidism?

A

post-thyroidectomy ‘stunning’Idiopathic- Abs to PTH-autoimmune parathyroid agenesis (DIGeorge syndrome)hypomagnesaemia, hyperphosphatemia

33
Q

Other rare causes of hypocalcemia?

A

acute pancreatitis in which free fatty acids chelate calciummassive transfusion in which infusion of citrate will complex calciumTLS or rhabdomyolysis in which phosphate released binds to ionized calciumSevere sepsisMeds- phospahte, bisphosphonatesHungry bone syndrome

34
Q

What is Hungry bone syndrome?

A

in cases of chronic hyperparathyroidism where the bone is continuously being resorbed, when calcium is given, bone very actively tries to take it up resulting in hypocalcemia

35
Q

Ddx with hypocalcemia and low PTH?

A

hypoparathyroidismMagnesium deficiency (diarrhea, malabsorption, alcoholism)

36
Q

Ddx with hypocalcemia and highPTH?

A

vitD deficiencyrenal failurevitD or PTHresistancephosphate excess

37
Q

What is pseudohypoparathyroidism?

A

decreased end organ responsiveness to PTH (PTH resistance)

38
Q

What causes pseudohypoparathyroidism?

A

molecular defects in the ability of PTH stimulate intracellular signaling pathways due to mutations in Gs alpha subunit (GNAS1) or downstream elements

39
Q

How doespseudohypoparathyroidism present in labs?

A

LABS: highly elevated PTH with hypocalcemia, hyperphosphatemia

40
Q

How doespseudohypoparathyroidism present clinically?

A

short stature, rounded face, foreshortened 4th/5th metacarpals, obesity (Albright’s Hereditary Osteodystrophy)- only some subtypes

41
Q

What is PHP 1a? MOI?

A

Defect in Gs alpha subunitsignaling causes unresponsiveness of the kidneys to PTH leading todecreased urinary cAMP and PO4, AHO phenotype and other hormonal defects such as decreased mentation, olfaction, TSH, glucagon, and LH/FSHDefect must be inherited from mother due to imprintingMOI: AD

42
Q

What is PHP 1b?

A

Same as PHP 1a but no AHO

43
Q

What is PHP 1c?

A

Same as PHP1a but the defect is downstream to Gs alpha subunit. AHO phenotype present

44
Q

What is Pseudopseudohypoparathyroidism?

A

physical exam feastures of AHO but without end-organ PTH resistance.Occurs when defective Gs protein alpha-subunit is inherited from the FATHER

45
Q

What is PHP2?

A

Defect in PKA that leads to normal urinary cAMP, decreased urinary phosphate, and no AHO phenotype

46
Q

How is acute hypocalcemia crises treated in the short term?

A

–Always correct Magnesium if low–Calcium Gluconate•1 - 2 ampules over ~10 – 20 minutes•Followed by infusion if indicated

47
Q

How is hypocalcemia treated in the longterm?

A

–Oral Calcium salts–Vitamin D replaced•Ergocalciferol/Cholecalciferol (act in 10-14 days) - effective only if PTH is present•Calcitriol – active vitamin D–Hydrochlorothiazide – increases reabsorption of Calcium in the distal tubule

STEP Pathology (80 decks)

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