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Endocrinology Exam 3 > Parathyroid and Mineral Metabolism Disorders > Flashcards

Parathyroid and Mineral Metabolism Disorders Flashcards

1
Q

Bones generally have two layers:

A

○ Spongy Trabecular Bone
■ Has open, cell-filled areas between struts of calcified lattice.
○ Compact Bone
■ Provides strength and is formed by concentric dense layers.

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2
Q

Present in the bone are three cell types:

A

Osteoblasts, Osteocytes, Osteoclasts

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3
Q

Osteoblasts physiology

A

○ Specialized Bone-forming cells
○ Produce Osteoid, a mixture of collagen and other proteins to which Hydroxyapatite binds
■ Calcium Phosphate is the most common form of
Hydroxyapatite

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4
Q

Osteocytes

A

A less active, “retired” Osteoblast cell

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5
Q

Osteoclasts

A

○ Large, multi-nucleated, mobile cells derived from Hematopoietic stem cells.
○ Responsible for Dissolving Bone

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6
Q

_____% of our Ca 2+ is stored in bone

A

99

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7
Q

Calcium has several important
physiologic functions in the body

A

○ Cellular signalling
○ Part of intercellular cement that holds
cells together at tight junctions
○ Cofactor in the coagulation cascade
○ Concentration gradient in neurons
affecting the excitability of the cell

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8
Q

Calcium Balance: intake vs. output

A

○ Intake: Ingestion and absorption in the small intestine.
■ Absorption is hormonally regulated.
○ Output: Primarily through the kidneys.
■ Ionized calcium is freely filtered at the glomerulus and some degree is reabsorbed along the tubules.
● Reabsorption is hormonally regulated.

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9
Q

Abosorption and reabsorption of calcium is ______ regulated

A

hormonally

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10
Q

Calcitriol (Vitamin D3)

A

From diet or made in skin

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11
Q

There are three main hormones that control Calcium balance

A

○ Parathyroid Hormone: Secreted by Parathyroid
○ Calcitriol (Vitamin D3): From diet or made in skin
○ Calcitonin: Secreted by Thyroid

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12
Q

The Parathyroid Glands

A

Four small endocrine glands located on the
back of the Thyroid in the deep tissue of the neck

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13
Q

Parathyroid gland Secrete Parathyroid
Hormone in response to ____ serum calcium

A

low

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14
Q

_____ in the cell membrane of Parathyroid cells detect the presence of serum Calcium

A

Calcium-Sensing Receptors (CaSR)

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15
Q

Low concentration of serum Calcium triggers
Parathyroid cells to increase production and
secretion of ____

A

PTH

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16
Q

Increasing Ca 2+ levels = _____ feedback

A

Negative

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17
Q

Secreted PTH dissolves in plasma and heads to
its target tissues: - _____

A

Bone, Kidney, Intestine*

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18
Q

PTH Function Increases _____ activity
in the bones. (paracrines)

A

osteoclast

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19
Q

_____ Increases renal tubular
reabsorption of calcium

A

PTH Function

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20
Q

What about Phosphate?

A

It is the 2nd key ingredient in the Hydroxyapatite of bone
■ Calcium Phosphate

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21
Q

PTH causes increased osteoclastic activity, releasing both _____ and _____ from bone

A

Calcium; Phosphate

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22
Q

However, PTH also inhibits renal reabsorption of
_____, keeping it at normal levels

A

Phosphate

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23
Q

Keeping Phosphorus levels within normal limits is a balancing act between ____ and _____

A

PTH; Vitamin D3

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24
Q

Also known as 1,25-Dihydroxycholecalciferol (1,25(OH) 2 D3 ). The active form of Vitamin D3

A

Calcitriol

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25
Q

Where does Calcitriol come from

A

Our body makes Calcitriol from Vitamin D obtained through our diet (fatty fish) or made in the skin by the action of sunlight

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26
Q

Calcitriol ____ serum Calcium level

A

increases

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27
Q

Low Ca 2+ levels trigger PTH secretion.
PTH stimulates ____ synthesis at
the kidney

A

Calcitriol

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28
Q

Calcitonin is released from the Thyroid in response to ____ levels of serum Ca 2+

A

Elevated

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29
Q

Why would calcitonin want to decrease bone resorption by inhibiting Osteoclasts?

A

It wants to increase bone building by osteoblasts

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30
Q

Most common cause of Primary Hyperparathyroidism

A

About 80% of cases due to Parathyroid Adenoma

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31
Q

Most common cause of hypercalcemia

A

Primary Hyperparathyroidism

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32
Q

Hyperparathyroidism

A

Overactive Parathyroid Gland(s)

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33
Q

Secondary Hyperparathyroidism causes

A

■ Chronic Kidney Disease
■ Significant Vitamin D Deficiency

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34
Q

Parathyroid Adenoma

A

○ Most common cause of Hyperparathyroidism.
○ Benign neoplasm of the Parathyroid Gland(s).
○ Usually diagnosed when the patient displays symptoms of hypercalcemia or when elevated serum calcium is found on routine blood work. Almost never palpable

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35
Q

Parathyroid Hyperplasia

A

○ Diffuse enlargement of all Parathyroid tissue.
○ May be familial (~10% of cases) or random.
○ MEN 1 or 2, or Isolated Familial Hyperparathyroidism

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36
Q

Parathyroid Carcinoma

A

○ Very rare cause of hyperparathyroidism.
○ About half of these tumors are palpable.
○ Usually very high PTH and Calcium levels

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37
Q

Secondary to Chronic Kidney Disease, Kidney failure leads to decreased ability to

A

■ Reabsorb Calcium
■ Excrete Phosphate
■ Produce Calcitriol

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38
Q

Hyperparathyroidism S&S

A

○Most people are asymptomatic or only mild symptoms
○“Bones, Stones, Abdominal Groans, Psychic Moans, and Fatigue Overtones.”
○ loss of cortical bone (decreased bone density)

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39
Q

Laboratory Findings of Hyperparathyroidism

A

○ High serum Calcium
○ Increased urinary Calcium
○ Decreased (or normal) serum Phosphorus
○ Increased serum Parathyroid Hormone - Confirms Dx
○ Increased 1,25-Dihydroxy-Vit D (Primary)

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40
Q

What confirms the diagnosis for hyperparathyroidism?

A

Increased serum Parathyroid Hormone

41
Q

Imaging Studies for hyperparathyroidism

A

Sestamibi Parathyroid Scan: “Mibi Scan”, Nuclear medicine scan performed to localize a Parathyroid Adenoma
○ Parathyroid Ultrasound: not as speficic as Mibi
○ MRI/CT: Not as helpful, mostly used if previous neck surgery
● Skull radiograph from a patient with severe secondary hyperparathyroidism due to prolonged end-stage renal disease - Renal Osteodystrophy

42
Q

Hyperparathyroidism treatment

A

depends on the cause.
○ Since most cases are due to Parathyroid
Adenomas, surgery (Parathyroidectomy) is
Tx of choice

43
Q

T/F in Parathyroid surgery, Because Parathyroid Hormone is essential for life, some Parathyroid needs to be left behind

A

T

44
Q

Other Treatments for Hyperparathyroidism

A

○ IV fluids to dilute the hypercalcemia is important.
○ Calcitriol: Can be given in Vitamin D deficiency.
○ Phosphate Regulators: To treat Hyperphosphatemia seen in CKD.
○ Cinacalcet: A calcimimetic agent, Binds to PTH-secreting cells, turning down PTH production
○ Bisphosphonates: V forms can be used in significant hypercalcemia

45
Q

Phosphate Regulators

A

● Calcium acetate (PhosLo)
● Lanthanum (Fosrenol)
● Sevelamer (Renagel)

46
Q

Phosphate Regulators MOA

A

Binds to phosphate in the small intestine, rendering it insoluble, forcing it to be excreted in the feces.

47
Q

Phosphate Regulators Indications

A

Hyperphosphatemia in End Stage Renal Disease
■ A form of Secondary Hyperparathyroidism

48
Q

Contraindications of Phosphate regulators

A

○ Hypophosphatemia
○ GI obstruction/Ileus
○ Calcium Acetate→ Hypercalcemia
and Kidney Stones

49
Q

Side Effects (minor) of Phosphate regulators

A

○ GI upset- Nausea, vomiting, diarrhea, abdominal pain
○ Calcium Acetate→ Hypercalcemia and Kidney Stones

50
Q

Adverse Reactions (Major) Of Phosphate regulators

A

○ Fecal impaction
○ Gastrointestinal Obstruction

51
Q

Follow up and Monitoring of Phosphate regulators

A

○ All are considered relatively safe during pregnancy
○ Lactation safety is unknown
○ With Calcium Acetate, monitor serum Ca 2+ twice weekly
until stable, then periodically.
○ Monitor phosphorus level

52
Q

Hypoparathyroidism

A

Underactive Parathyroid Glands.
○ Hyposecretion of the Parathyroid Hormone

53
Q

Causes of Hypoparathyroidism can be

A

○ Acquired - More common
○ Congenital

54
Q

Acquired Hypoparathyroidism causes

A

○ 5-10% of patients status post Thyroidectomy
○ Can occur after a Parathyroidectomy
○ Radiation to the neck is sometimes a cause
○ Rare autoimmune attack on the parathyroids
○ Damage to gland by heavy metal poisoning (copper, iron)
○ Magnesium Deficiency or Excess: Inhibits secretion of PTH

55
Q

Congenital Hypoparathyroidism

A

○ Not common, occurring in less than 1 in 70,000 people.
○ Causes hypocalcemia beginning in infancy.
■ May go undetected for several years in mild case

56
Q

Congenital Hypoparathyroidism typically presents in infancy as _____

A

hypocalcemic seizures.

57
Q

Signs and Symptoms of Hypoparathyroidism

A

■ Muscle cramps and exaggerated DTRs
■ Irritability, Altered Mental Status
■ Tingling in the circumoral area, hands, and feet
■ Severe- Tetany, convulsion, and stridor

58
Q

Physical Exam Findings of hypoparathyroidism

A

○ Chvostek Sign:
■ Hyperexcitable Facial Nerve due to hypocalcemia.
○ Trousseau Sign:
■ Carpal Spasm due to hypocalcemic tetany.

59
Q

Laboratory Findings in Hypoparathyroidism

A

○ Low serum Calcium
○ If Albumin level is abn., calculate the Adjusted Calcium
○ Decreased urinary Calcium
○ Increased serum Phosphate
○ Low serum Parathyroid Hormone - Confirms Dx
○ May have Low Serum Magnesium level

60
Q

CT of the head may show
calcifications of the basal ganglia with

A

Hypoparathyroidism

61
Q

EKG may show QT prolongation with

A

Hypoparathyroidism

62
Q

Treatment of hypoparathyroidism

A

○ Airway protection - Beware of laryngeal tetany!
○ Treat tetany with slow administration of IV Calcium
Gluconate.
○ Oral Calcium (liquid, chews, tabs) to be given as soon as possible to help maintain.
■ Vitamin D3 or Calcitriol to be co-administered.
○ If Magnesium level is low, correct this to enhance
parathyroid hormone secretion.
○ Parathyroid transplantation can work for post op Pts

63
Q

Rx -Calcium MOA

A

Calcium replacement

64
Q

Rx- Calcium

A

Calcium Gluconate (IV) and Calcium Carbonate (PO)

65
Q

Contraindications of Rx - calcium

A

○ Hypercalcemia
○ Hypophosphatemia
○ Nephrolithiasis
○ Digitalis toxicity

66
Q

Side effects of Rx - calcium

A

○ Constipation, nausea
○ IV only- Vasodilation, hypotension, dizziness,
flushing, syncope

67
Q

Adverse Reactions for Rx - Calcium

A

○ Milk-Alkali Syndrome (Supplement-induced hypercalcemia)
○ Nephrolithiasis

68
Q

Follow up and Monitoring for Rx- Calcium

A

○ May use during pregnancy, probably safe with lactation
○ Monitor serum Calcium closely (especially with the IV form)
○ Monitor for signs for hypercalcemia with thorough history

69
Q

Many malignant tumors can produce ____

A

Hypercalcemia

70
Q

These (malignancy and calcium) tumors secrete a substance we call
_____

A

PTH-related protein (PTHrP)

71
Q

PTHrP functions like PTH, leading to
_____ and _____

A

hypercalcemia; hypophosphatemia

72
Q

_____ deficiency can lead to Hypocalcemia

A

Vitamin D

73
Q

Rx- Vitamin D MOA

A

Stimulates calcium and phosphorus intestinal absorption and promotes bone mineralization

74
Q

Indications of Rx- Vitamin D

A

○ Vitamin D deficiency
○ Postmenopausal Osteoporosis (Prevention and Tx)

75
Q

Contraindications for Rx- Vitamin D

A

Hypercalcemia

76
Q

Side Effects of Rx - Vitamin D

A

Nausea, vomiting, abdominal pains, anorexia

77
Q

Adverse Reactions of Rx - Vitamin D

A

Hypercalcemia (“bones, stones, abdominal groans,
psychic moans, fatigue overtones”, etc.)

78
Q

Follow up and Monitoring Rx- Vitamin D

A

○ Safe in pregnancy if at recommended lower doses
■ Teratogenicity if taken at high doses
○ Safe in Lactation
○ Monitor creatinine/BUN, Calcium, Phosphate

79
Q

Important determinants of serum Phosphorus levels

A

Renal excretion and intestinal absorption

80
Q

Hyperphosphatemia cause

A

Advanced chronic kidney disease with decreased renal phosphate excretion is by far the most common cause

81
Q

Treatment of Hyperphosphatemia is two fold

A

■ Optimize Tx of kidney disease
■ Consider treating with
Phosphate binders
○ Dialysis can improve serum
hyperphosphatemia

82
Q

Hypophosphatemia causes

A

Can be caused by dozens of deranged metabolic processes
■ Ex: Meds, Diabetes, poor absorption, renal problems

83
Q

Severe hypophosphatemia can lead to ____

A

tissue hypoxia and even rhabdomyolysis

84
Q

Rx- Phosphorus MOA

A

Phosphorus replacement

85
Q

Contraindications of Rx - Phosphorus

A

○ Hypoparathyroidism
○ Advanced chronic kidney disease

86
Q

Adverse Reactions of Rx - Phosphorus

A

Hyperphosphatemia

87
Q

Follow up and Monitoring for Rx - Phosphorus

A

Monitor serum phosphate and calcium levels closely, especially if administering via IV

88
Q

Hypermagnesemia cause

A

○ Typically due to advanced CKD with impaired renal excretion.
○ May be secondary to Magnesium replacement or pregnant
women treated for Preeclampsia/Eclampsia

89
Q

High Mg 2+ characteristically results in____

A

muscle weakness, mental
obtundation, and confusion

90
Q

___ is usually necessary to remove Magnesium in
those with severe kidney disease

A

Hemodialysis

91
Q

Most common causes of Hypomagnesemia

A

Diuretics, Diarrhea, Alcoholism

92
Q

Low Magnesium causes inhibition of ___ release

A

PTH

93
Q

Rx- Magnesium MOA

A

Magnesium replacement/supplementation

94
Q

Rx- Magnesium Indications

A

○ Low Magnesium (PO for mild, IV for symptomatic)
○ IV- Torsades de pointes, Preeclampsia/Eclampsia seizures

95
Q

Contraindications of Rx - Magnesium

A

○ PO version- Ulcerative colitis, diverticulitis, colostomy
○ IV version- Myocardial damage, heart block

96
Q

Side Effects of Rx - Magnesium

A

○ PO version- Nausea, vomiting, diarrhea
○ IV version- Drowsiness, diaphoresis, flushing

97
Q

Adverse Reactions of Rx - Magnesium

A

○ PO version- None reported
○ IV version- Cardiac depression, Pulmonary edema

98
Q

Follow up and Monitoring of Rx- Magnesium

A

○ PO version is safe in pregnancy. Use caution with IV version.
■ Minimal fetal risk if used for less than 5 days
○ Check creatinine at baseline.
○ Monitor Magnesium level and kidney function while on med

Endocrinology Exam 3 (6 decks)

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