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Endocrinology > Parathyroid > Flashcards

Parathyroid Flashcards

1
Q

Photoisomerization

A

Of provitamin D in the skin to vitamin D3

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2
Q

Where is vitamin D stored?

A

Mostly the liver, somewhat in adipose

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3
Q

Cholecalciferol

A

VItamin D3
Formed in the skin
Converted to 25-hydroxy vitamin D in liver

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4
Q

1,25-dihydroxycholecalciferol

A

Calcitriol
Formed in proximal tubules of kidney
Most active form of vitamin D
This step stimulated by PTH

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5
Q

When calcium levels rise, phosphate levels?

A

Lower.

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6
Q

Hypocalcemia stimulates?

A

PTH, increases activity of alpha-1-hydroxylase in the kidney

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7
Q

Functions of calcitriol

A 
Binds to single vitamin D receptor
Promotes intestinal absorption of Ca2+
Stimulates phosphate absorption
Direct suppression of PTH
Allows PTH induced osteoclast activity
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8
Q

Vitamin D Deficiency

A

Reduced absorption of Ca and Phosphorus
Persistent:
Hypocalcemia causes hyperparathyroidism
Bone issues

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9
Q

What medication used chronically can inhibit intestinal vitamin D absorption?

A

Glucocorticoids in high doses

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10
Q

Vitamin D deficiency etiology

A 
Elderly
Winter/housebound
Chronic renal dz
GI dz:  malabs
Liver failure
Drugs
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11
Q

Vitamin D Toxicity

A 
Excess vitamin D supplementation
Hypercalcemia, hypercalciuria
Polyuria, polydipsia
Confusion
Anorexia, vomiting
Muscle weakness, bone demineralization
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12
Q

Calcium Physiology

A

Partially absorbed in intestines with help of calcitriol.
Filtration in kidneys
.05% bound to albumin

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13
Q

99% of calcium remains in bone as?

A

Hydroxyapatite

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14
Q

Functions of Calcium

A

Contraction of all muscle
Clotting cascade
Transmission of nerve signals

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15
Q

___% of phosphate is stored in the bone.

A

85%

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16
Q

Bone remodeling cycle

A

Resorption (2 weeks)
Reversal (4-5 wks)
Formation (4 months)

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17
Q

Stress on a bone stimulates?

A

Osteoblast activity in bones

Makes them stronger and less brittle

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18
Q

intermittently secreted PTH stimulates bone _____?

A

Formation

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19
Q

Constantly secreted PTH stimulates?

A

Bone resorption.

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20
Q

Osteomalacia

A

Poor bone calcification

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21
Q

Osteopenia

A

Diminished organic bone matrix

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22
Q

PTH is almost entirely produced and secreted by what cells?

A

Chief cells

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23
Q

Which embryological pouches are parathyroid glands derived from?

A

3rd and 4th branchial pouches

24
Q

PTH is the main player in ______ and _____ homeostasis in the body.

A

Calcium and Phosphate

25
Q

How long is PTH half-life once excreted?

A

Minutes

26
Q

What metabolizes PTH?

A

The liver and kidney

Degrades to C-terminal fragments

27
Q

Parathyroid cells have a _____ ______ receptor.

A

Calcium-sensing

The kidneys also have these for handling by the renal tubules.

28
Q

Hyperphosphatemia stimulates _________ secretion.

A

PTH

Lets phosphate be excreted form the kidneys while keeping Ca in.

29
Q

________ also contain Vitamin D receptors.

A

Parathyroid

Inhibits PTH synthesis

30
Q

PTH-Related Protein (PTHrP)

A

Secreted by nonmetastatic tumors
Causes secondary hyperparathyroidism
Increases bone resorption
Does not increase Ca absorption in the intestines

31
Q

Calcitonin is secreted by?

A

Parafollicular cells of the thyroid
Stimulated by high Ca levels
Decreases Plasma Ca
Decreases bone resorption

32
Q

Primary Hyperparathyroidism (HPT) Etiology

A

Parathyroid adenoma
Hyperplasia
Parathyroid carcinoma

33
Q

Primary HPT presentation

A

Hypercalcemia
Decreased bone density
HTN
Left ventricular hypertrophy

34
Q

Secondary HPT

A

Malignancy (MM, lung, kidney)

Labs: PTHrP

35
Q

Milk-alkali syndrome

A

High intake of milk or calcium

36
Q

Medications causing hypercalcemia:

A 
Lithium (increased secretion PTH)‏
Thiazide diuretics (lower urinary Ca2+ excretion)
Thyroid hormone
Estrogens and progesterones
Hypervitaminosis A
Hypervitaminosis D
37
Q

Manifestations of hypercalcemia?

A

Bones, stones abdominal pain and psychic groans.

38
Q

Symptoms of Hypercalcemia

A

Polydipsia, polyuria, dehydration
Bradycardia, short QT, arrhythmias
Muscle weakness
Renal insufficiency

39
Q

Physical findings of hypercalcemia

A

Usually none unless malignancy

40
Q

Hypercalcemia Labs

A 
Serum calcium (normal= 8.2-10.2)
Ionized calcium (normam= 1.15-1.35)
Serum Phosphate:  Inverse of Ca (2.5-4.5)
41
Q

Evelevated Ca should be confirmed by?

A

Two readings corrected to albumin level.

42
Q

Primary HPT Mgmt

A

If progressive and symptomatic: surgery

43
Q

Asymptomatic HPT mgmt

A 
Avoid meds that worsen it
Low calcium diet
Physical activity
Adequate hydration
Adequate vitamin D
44
Q

Medications to manage asymptomatic HPT

A

Biphosphonates (Pamidronate, Zoledronate)
Calcimimetic (activated calcium sensing receptor)
Dialysis is last resort

45
Q

Hypercalcemic Crisis

A

Saline Diuresis (250-500mL/hr)
IV calcitonin
IV biphosphonates

46
Q

Hypocalcemia Symptoms

A 
Parasthesias 
Hyperventilation
Myalgias, muscle cramps
Fatigue, anxiety
Tetany, seizures, myopathy
Hypotension
Papilledema
Prolonged QT
47
Q

Etiology of Hypocalcemia

A

HypoPTH: from surgery, autoimmune
Hypovitaminosis D
Hyerphosphatemia

48
Q

Hypocalcemia labs

A

Decreased Ca, Increased Phosphate
Low calcitriol levels
High PTH levels (usually)

49
Q

Hypocalcemia Tx

A

Vitamin D supplement + calcium
600-1200 mg calcium/day
Can add thiazide diuretic
Watch for hypercalcemia

50
Q

Trousseau’s Sign

A

Wrist turning down when BP cuff applied.

Unique to Hypocalcemia

51
Q

Hyperphosphatemia

A

Marked tissue breakdown
Lactic acidosis
Renal failure**
Vitamin D toxicity

52
Q

Hyperphosphatemia Tx

A

Saline infusion
Dialysis
Low phosphate diet

53
Q

Hyperphosphatemia Causes

A

Insulin admin in DKA
Refeeding malnourished pt’s
Acute resp. alkalosis

54
Q

Hyperphosphatemia S/S

A

Parasthesias, irritability, seizures, coma
CHF
Proximal myopathy, dysphagia, ileus, rhabdo

55
Q

Hyperphosphatemia Tx

A

Normal dietary intake
Treat underlying result
Vitamin D if due to deficiency

Endocrinology (16 decks)

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