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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
How long is PTH half-life once excreted?
Minutes
26
What metabolizes PTH?
The liver and kidney | Degrades to C-terminal fragments
27
Parathyroid cells have a _____ ______ receptor.
Calcium-sensing | The kidneys also have these for handling by the renal tubules.
28
Hyperphosphatemia stimulates _________ secretion.
PTH | Lets phosphate be excreted form the kidneys while keeping Ca in.
29
________ also contain Vitamin D receptors.
Parathyroid | Inhibits PTH synthesis
30
PTH-Related Protein (PTHrP)
Secreted by nonmetastatic tumors Causes secondary hyperparathyroidism Increases bone resorption Does not increase Ca absorption in the intestines
31
Calcitonin is secreted by?
Parafollicular cells of the thyroid Stimulated by high Ca levels Decreases Plasma Ca Decreases bone resorption
32
Primary Hyperparathyroidism (HPT) Etiology
Parathyroid adenoma Hyperplasia Parathyroid carcinoma
33
Primary HPT presentation
Hypercalcemia Decreased bone density HTN Left ventricular hypertrophy
34
Secondary HPT
Malignancy (MM, lung, kidney) | Labs: PTHrP
35
Milk-alkali syndrome
High intake of milk or calcium
36
Medications causing hypercalcemia:
``` Lithium (increased secretion PTH)‏ Thiazide diuretics (lower urinary Ca2+ excretion) Thyroid hormone Estrogens and progesterones Hypervitaminosis A Hypervitaminosis D ```
37
Manifestations of hypercalcemia?
Bones, stones abdominal pain and psychic groans.
38
Symptoms of Hypercalcemia
Polydipsia, polyuria, dehydration Bradycardia, short QT, arrhythmias Muscle weakness Renal insufficiency
39
Physical findings of hypercalcemia
Usually none unless malignancy
40
Hypercalcemia Labs
``` Serum calcium (normal= 8.2-10.2) Ionized calcium (normam= 1.15-1.35) Serum Phosphate: Inverse of Ca (2.5-4.5) ```
41
Evelevated Ca should be confirmed by?
Two readings corrected to albumin level.
42
Primary HPT Mgmt
If progressive and symptomatic: surgery
43
Asymptomatic HPT mgmt
``` Avoid meds that worsen it Low calcium diet Physical activity Adequate hydration Adequate vitamin D ```
44
Medications to manage asymptomatic HPT
Biphosphonates (Pamidronate, Zoledronate) Calcimimetic (activated calcium sensing receptor) Dialysis is last resort
45
Hypercalcemic Crisis
Saline Diuresis (250-500mL/hr) IV calcitonin IV biphosphonates
46
Hypocalcemia Symptoms
``` Parasthesias Hyperventilation Myalgias, muscle cramps Fatigue, anxiety Tetany, seizures, myopathy Hypotension Papilledema Prolonged QT ```
47
Etiology of Hypocalcemia
HypoPTH: from surgery, autoimmune Hypovitaminosis D Hyerphosphatemia
48
Hypocalcemia labs
Decreased Ca, Increased Phosphate Low calcitriol levels High PTH levels (usually)
49
Hypocalcemia Tx
Vitamin D supplement + calcium 600-1200 mg calcium/day Can add thiazide diuretic Watch for hypercalcemia
50
Trousseau's Sign
Wrist turning down when BP cuff applied. | Unique to Hypocalcemia
51
Hyperphosphatemia
Marked tissue breakdown Lactic acidosis Renal failure** Vitamin D toxicity
52
Hyperphosphatemia Tx
Saline infusion Dialysis Low phosphate diet
53
Hyperphosphatemia Causes
Insulin admin in DKA Refeeding malnourished pt's Acute resp. alkalosis
54
Hyperphosphatemia S/S
Parasthesias, irritability, seizures, coma CHF Proximal myopathy, dysphagia, ileus, rhabdo
55
Hyperphosphatemia Tx
Normal dietary intake Treat underlying result Vitamin D if due to deficiency

Endocrinology (16 decks)

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