BC: Lecture 5 Flashcards by Becca Kessler

How does chronic kidney disease affect calcium and phosphate homeostasis?

By disrupting the Ca and Pi reabsorption process

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What defines hypocalcemia?

When total serum calcium concentrations are less than 8.5 mg/dL
Or serum ionized calcium less than 4.4 mg/dL

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What are the symptoms of hypocalcemia?

Muscle cramps
Increased neuromuscular excitability Muscle spams
Fatigue
Cardiac dysfunction
Depression, psychosis, seizures

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what is hypoparathyroidism?

Undersecretion of PTH

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what leads to hypoparathyroidisms?

Hypocalcemia that also has serum PTH that is really low

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what are the common causes of hypoparathyroidisms?

autoimmune

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what is DiGeorges syndrome?

Congenital disease that causes a lack of the parathyroid glan

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How can you treat hypoparathyroidism?

Calcium and calcitriol supplements

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Is hypoparathyroidism associated with CaSR mutations?

yes

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how is hypoparathyroidism associated with CaSR mutations?

By consitutively activating CaSR causing hypocalcemia since PTH becomes
inhibited leading to low Ca reabsorption

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How do you treat hypoparathyroidism?

Calcium and calcitriol

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What causes pseudohypoparathyroidism?

Hypocalcemia due to lack of sensitivity to PTH on tissues

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What occurs in this disease (hypocalcemia)?

Serum PTH is high to overcome the resistance to increase low Ca levels

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How does a lack of Vit. D inhibit Ca and Pi uptake?

Due to calcium transport proteins relying on Vit D to function, so without it they do
not work

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what can a Vit. D deficiency lead to in children?

rickets

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what can a Vit. D deficiency lead to in adults?

Osteomalacia

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what are the two types of Vit. D deficient rickets?

Type 1
Type 2

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what is VDDR type 1?

Pseudovitamin D deficiency

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what causes VDDR type I

Defect in renal 25-OH-Vit. D 1-alpha hydroxylase

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Is 1,25(OH)2D3 high or low in VDDR type 1?

very low

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What is VDDR type 2?

a. Hereditary vitamin D resistant rickets

What causes VDDR type 2?

Defect in Vit. D receptor

what defines hypercalcemia?

Serum total calcium >10.5 mg/dL
Ionized calcium >5.4 mg/dL

what are the symptoms of hypercalcemia?

Fatigue
EKG abnormalities
Nausea, vomiting, constipation Anorexia
Abdominal pain
Hypercaciuria
Calcification of soft tissues Hypercalcemic crisis

Is 1,25(OH)2D3 high or low in VDDR type 2?

High

what causes primary hyperparathyroidism?

Oversecretion of PTH without a negative feedback on it

How do you treat primary hyperparathryoidism?

surgery

what can primary hyperparathyroidism cause?

Hypercalcemia Low Pi High bone turnover Kidney stones

What are the two types of familial primary hyperparathryoidism?

MEN1 (Mutiple Endocrine Neoplasia) b. MEN2A

What occurs in MEN1?

Menin tumor suppressor gene inactivated

What occurs in MEN2A?

Gain of function mutation in RET protooncogene

Can inactivating mutations of CaSR cause familial primary hyperparathryoidism?

yes

What occurs to cause familial primary hyperparathryoidism in this instance?

CaSR inactive so high Ca levels are not sensed leading to elevated PTH since parathyroid gland reads Ca levels as low

What causes hypercalcemia of malignancy?

Tumors that secrete factors that stimulate bone resorption

Is secondary hyperparathyroidism a condition of hypercalcemia?

What occurs in this disease (hypercalcemia)?

Oversecretion of PTH due to hypocalcemia or decreased 1,25(OH)2D3 b. Renal failure

How does renal failure cause hypercalcemia?

Due to the kidneys being unable to produce 1,25(OH)2D3 which inhibits PTH

what defines hypophosphatemia?

<2.5-4.5 mg/dL of Pi

what is X-linked hypophosphatemic rickets (XLH)?

PHEX gene on X-chromosome gets mutated causing bone deformities

what does PHEX normally do?

Inhibits FGF23 production

what does XLH mutation do?

Causes inactive PHEX so FGF23 is increased

What causes autosomal dominant hypophosphatemic rickets?

Mutations in FGF23 causing its increase

How do you treat XLH?

. Phosphate supplementation b. High calcitriol

What are the two forms of hypophosphatemic rickets?

Autosomal dominant b. Autosomal recessive

What causes autosomal recessive hypophosphatemic rickets?

a.Mutations in DMP1 i. Causes overproduction of FGF23

What causes hereditary hypophosphatemic rickets?

Loss of function mutations in NaPiIIc

What is tumor induced osteomalacia?

An acquired syndrome of renal phosphate wasting

What does the condition cause?

Secretion of factors into the blood like FGF23

what defines hyperphosphatemia?

Phosphate > 4.5mg/dL or >1.5mM

what are the symptoms of acute hyperphosphatemia?

Hypocalcemia

what are the symptoms of chronic hyperphosphatemia?

Soft tissue calcification Renal failure