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Endocrine > Calcium and Vitamin D Disorders > Flashcards

Calcium and Vitamin D Disorders Flashcards

1
Q

45% of serum calcium is bound to…

A

protein, primarily albumin. Albumin levels will alter serum calcium levels

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2
Q

If the pH were in a state of alkalosis what would happen to the binding of albumin?

A

increased binding to albumin

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3
Q

If the pH were in a state of Acidosis what would happen to the binding of albumin?

A

decreased binding to albumin

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4
Q

What is Calcium regulated by?

A

PTH, vit D via effects on bone , kidney and GI tract

Negative inhibition by acting on Ca Sensing receptor (CaSR)
At level of PTH gland-inhibits release of PTH
Kidney: inc excretion of calcium, dec calcium reabsorption

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5
Q

Primary hyperparathyroidism is most commonly cause by what?

A

85% single adenoma

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6
Q

Where does most of the loss of BMD in PHPTH occur?

A

lumbar spine

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7
Q

What are the guidelines for surgical management of Asymptomatic HPTH?

A

Plasma calcium >1.0 mg/dL of the ULN
Calculated Cr C <50 years

Monitoring:
Yearly serum Ca++
Yearly Plasma Cr
BMD every 1-2 years

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8
Q

Preoperative localization for PHTPH

A

Done once a diagnosis is made and pt to have surgery
Sestamibi scan
US neck
CT neck

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9
Q

What are the treatment guidelines for hypercalcemia?

A

Ca< 12-14 mg/dL: may be tolerated chronically and may not require immediate therapy

Calcium >14 mg/dL requires therapy, regardless of symptoms

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10
Q

How do we treat hypercalcemia?

A

IV hydration:
Saline 200-300 ml/hr
Adjust to keep urine output 100-150mL/h

Diuresis with lasix only if signs of fluid overload

Calcitonin/Bisphosphonates

Use of Calcimimetics (inhibit PTH release)

Dialysis in some cases

Glucocorticoids when indicated

Identify/Treat underlying cause

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11
Q

Calcitonin

A

Osteoclast inhibitor/inc renal excretion

4IU/kg, IV or SC, Q12 hours
can be increased to 6-8 IU/kg Q6 hr
Nasal form not efficacious

Rapid reduction in calcium (within 4-6 hours)

Short lived effect-limited to initial 48 hrs
tachyphylaxis (poss receptor down-regulation)

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12
Q

Bisphosphonates

A

Pamidronate

Zolendronate

Osteoclast inhibitors

IV route

Expect reduction in serum calcium 24-36 hours

Duration of effects is variable

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13
Q

Cinacalcet

A

Calcimimetic- inc the sensitivity of the CaSR to extracellular calcium

Inhibits PTH release

Indications:
parathyroid cancer
secondary HPTH
non surgical primary HPTH with severe hypercalcemia

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14
Q

Pseudohypoparathyroidism

A

Resistance to PTH action

2/2 to defective signaling of PTH action via cell membrane receptor (G- protein)

Elevated PTH level, elevated phosphorus and low calcium

Also affects TSH, LH, FSH, GH signaling

Autosomal Dominant gene mutation of GNAS1 ( alpha subunit of G protein):

G protein is unable to activate downstream signaling and end organ response to PTH

GNAS1 is imprinted in humans so what is expressed depends on how an allele was transmitted:

Maternal transmission (type 1 A): 
     -biochemical abnormalities + phenotypic features

paternal transmission (pseudo-pseudo): -phenotypic features only

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15
Q

Albright’s hereditary osteodystrophy

A

Most common type of pseudo-hypoparathyroidism (type 1 A)

Labs: Inc PTH, Inc phos and low Calcium and resistance to other G protein coupled hormones
Constellation of symptoms:
Short stature
Obesity
Round face
Developmental delay
Short metacarpals
4 and 5, dimples instead of knuckle
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16
Q

Clinical features of hypocalcemia

A 
Neuromuscular irritability
Paresthesias 
Chvosteks’ sign
Trousseau’s sign
Prolonged QT interval
Broncho, carpal or laryngeal spasm
Seizures
17
Q

Management of hypocalcemia

A

Indications for acute treatment

Symptoms present

Asymptomatic with:
Serum calcium <7.5 mg/dL
Hx of seizure
Abnormal EKG

18
Q

Emergency management of hypocalcemia

A

IV calcium gluconate ( less likely to cause tissue necrosis)
Cardiac monitoring
For immediate relief of symptoms:
-20 ml of 10% calcium gluconate diluted in 100-200 ml of NS or D5 infused over 10 min
- (10 ml=2.25mmol elemental calcium)
-transient effect, lasting 2-3 hrs
- need slow gtt to follow (40 ml of 10% calcium gluc in 1 L saline or D5 over 24 hrs )

19
Q

Management of chronic hypocalcemia

A

Manage underlying etiology

Oral calcium

- 1.0-1.5 g elemental calcium/day
- 1 gram oral calcium, (calcium carbonate) = 400 mg of elemental calcium

Oral vitamin D
-calcitriol preferred 0.25-0.5 mcg 1- 2x/day

Manage underlying etiology

Goal of therapy: calcium at or below the normal limit
Higher levels result in hypercalciuria

Oral calcium

- 1.0-1.5 g elemental calcium/day
- 1 gram oral calcium, (calcium carbonate) = 400 mg of elemental calcium

Oral vitamin D
-calcitriol preferred 0.25-0.5 mcg 1-2x/day

20
Q

Osteomalacia risks

A

Results from inadequate mineralization of bone

Decreased bone strength and increased risk for fracture

Osteomalacia- adult bone
Impaired mineralization of the bone matrix

Rickets – occurs in children at the epiphysis of the growing skeleton
Un-mineralized osteoid at the growth plate

21
Q

?

A

Rickets and osteomalcia occur together when growth plates are open

Only osteomalcia occurs after growth plate has closed

Results from inadequate calcium, phosphate or vitamin D

22
Q

Clinical features of osteomalacia

A 
Bone pain
Deformity
Fracture 
Proximal myopathy
Hypocalcemia (vit D def)
23
Q

clinical features of rickets

A 
Growth retardation
Bone pain, fractures in unusual locals (scapula, pubic rami)
Skeletal deformity
Bowing of long bones
Widening of the growth plates
24
Q

Vitamin D deficiency

A 
Decreased skin production
Elderly, housebound
Pigmented skin
sunscreen
Obese
Poor nutrition
 Malabsorption

Secondary hyperparathyroidism
Malabsorption
Gastric bypass
Drugs –phenytoin (inc metab of vit D)

25
Q

Lab findings for vit d def

A

25 OH D <15-20 (100%)

PTH elevated (100%)

Elevated Alkaline phosphatase

Low calcium, phosphorus

Low urinary calcium

26
Q

Symptoms associated with vit D deficiency

A

Bone pain (lower extremities, pelvis)

Muscle weakness

Fracture/osteomalacia

Waddling gait

Muscle spasms, cramps

Symptoms are insidious in onset

27
Q

Vit D replacement

A

Available forms: ergocalciferol (D2) and cholecalciferol (D3)

D3 preferred

For every 100 units of vid D added, serum 25 OH D should increase by 1.0 ng/ml

Can provide daily vs weekly vs monthly

If level is <20, would load once a week with 50, 000 IU x 6-8 weeks, followed by daily vit D to maintain

Repeat vit D level 1 month s/p load and again 3-4 months later

Aim to keep vit D in range of 30-50

Endocrine (8 decks)

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