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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
Where does Calcitriol come from
Our body makes Calcitriol from Vitamin D obtained through our diet (fatty fish) or made in the skin by the action of sunlight
26
Calcitriol ____ serum Calcium level
increases
27
Low Ca 2+ levels trigger PTH secretion. PTH stimulates ____ synthesis at the kidney
Calcitriol
28
Calcitonin is released from the Thyroid in response to ____ levels of serum Ca 2+
Elevated
29
Why would calcitonin want to decrease bone resorption by inhibiting Osteoclasts?
It wants to increase bone building by osteoblasts
30
Most common cause of Primary Hyperparathyroidism
About 80% of cases due to Parathyroid Adenoma
31
Most common cause of hypercalcemia
Primary Hyperparathyroidism
32
Hyperparathyroidism
Overactive Parathyroid Gland(s)
33
Secondary Hyperparathyroidism causes
■ Chronic Kidney Disease ■ Significant Vitamin D Deficiency
34
Parathyroid Adenoma
○ 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
35
Parathyroid Hyperplasia
○ Diffuse enlargement of all Parathyroid tissue. ○ May be familial (~10% of cases) or random. ○ MEN 1 or 2, or Isolated Familial Hyperparathyroidism
36
Parathyroid Carcinoma
○ Very rare cause of hyperparathyroidism. ○ About half of these tumors are palpable. ○ Usually very high PTH and Calcium levels
37
Secondary to Chronic Kidney Disease, Kidney failure leads to decreased ability to
■ Reabsorb Calcium ■ Excrete Phosphate ■ Produce Calcitriol
38
Hyperparathyroidism S&S
○Most people are asymptomatic or only mild symptoms ○“Bones, Stones, Abdominal Groans, Psychic Moans, and Fatigue Overtones.” ○ loss of cortical bone (decreased bone density)
39
Laboratory Findings of Hyperparathyroidism
○ High serum Calcium ○ Increased urinary Calcium ○ Decreased (or normal) serum Phosphorus ○ Increased serum Parathyroid Hormone - Confirms Dx ○ Increased 1,25-Dihydroxy-Vit D (Primary)
40
What confirms the diagnosis for hyperparathyroidism?
Increased serum Parathyroid Hormone
41
Imaging Studies for hyperparathyroidism
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
Hyperparathyroidism treatment
depends on the cause. ○ Since most cases are due to Parathyroid Adenomas, surgery (Parathyroidectomy) is Tx of choice
43
T/F in Parathyroid surgery, Because Parathyroid Hormone is essential for life, some Parathyroid needs to be left behind
T
44
Other Treatments for Hyperparathyroidism
○ 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
Phosphate Regulators
● Calcium acetate (PhosLo) ● Lanthanum (Fosrenol) ● Sevelamer (Renagel)
46
Phosphate Regulators MOA
Binds to phosphate in the small intestine, rendering it insoluble, forcing it to be excreted in the feces.
47
Phosphate Regulators Indications
Hyperphosphatemia in End Stage Renal Disease ■ A form of Secondary Hyperparathyroidism
48
Contraindications of Phosphate regulators
○ Hypophosphatemia ○ GI obstruction/Ileus ○ Calcium Acetate→ Hypercalcemia and Kidney Stones
49
Side Effects (minor) of Phosphate regulators
○ GI upset- Nausea, vomiting, diarrhea, abdominal pain ○ Calcium Acetate→ Hypercalcemia and Kidney Stones
50
Adverse Reactions (Major) Of Phosphate regulators
○ Fecal impaction ○ Gastrointestinal Obstruction
51
Follow up and Monitoring of Phosphate regulators
○ 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
Hypoparathyroidism
Underactive Parathyroid Glands. ○ Hyposecretion of the Parathyroid Hormone
53
Causes of Hypoparathyroidism can be
○ Acquired - More common ○ Congenital
54
Acquired Hypoparathyroidism causes
○ 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
Congenital Hypoparathyroidism
○ 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
Congenital Hypoparathyroidism typically presents in infancy as _____
hypocalcemic seizures.
57
Signs and Symptoms of Hypoparathyroidism
■ Muscle cramps and exaggerated DTRs ■ Irritability, Altered Mental Status ■ Tingling in the circumoral area, hands, and feet ■ Severe- Tetany, convulsion, and stridor
58
Physical Exam Findings of hypoparathyroidism
○ Chvostek Sign: ■ Hyperexcitable Facial Nerve due to hypocalcemia. ○ Trousseau Sign: ■ Carpal Spasm due to hypocalcemic tetany.
59
Laboratory Findings in Hypoparathyroidism
○ 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
CT of the head may show calcifications of the basal ganglia with
Hypoparathyroidism
61
EKG may show QT prolongation with
Hypoparathyroidism
62
Treatment of hypoparathyroidism
○ 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
Rx -Calcium MOA
Calcium replacement
64
Rx- Calcium
Calcium Gluconate (IV) and Calcium Carbonate (PO)
65
Contraindications of Rx - calcium
○ Hypercalcemia ○ Hypophosphatemia ○ Nephrolithiasis ○ Digitalis toxicity
66
Side effects of Rx - calcium
○ Constipation, nausea ○ IV only- Vasodilation, hypotension, dizziness, flushing, syncope
67
Adverse Reactions for Rx - Calcium
○ Milk-Alkali Syndrome (Supplement-induced hypercalcemia) ○ Nephrolithiasis
68
Follow up and Monitoring for Rx- Calcium
○ 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
Many malignant tumors can produce ____
Hypercalcemia
70
These (malignancy and calcium) tumors secrete a substance we call _____
PTH-related protein (PTHrP)
71
PTHrP functions like PTH, leading to _____ and _____
hypercalcemia; hypophosphatemia
72
_____ deficiency can lead to Hypocalcemia
Vitamin D
73
Rx- Vitamin D MOA
Stimulates calcium and phosphorus intestinal absorption and promotes bone mineralization
74
Indications of Rx- Vitamin D
○ Vitamin D deficiency ○ Postmenopausal Osteoporosis (Prevention and Tx)
75
Contraindications for Rx- Vitamin D
Hypercalcemia
76
Side Effects of Rx - Vitamin D
Nausea, vomiting, abdominal pains, anorexia
77
Adverse Reactions of Rx - Vitamin D
Hypercalcemia (“bones, stones, abdominal groans, psychic moans, fatigue overtones”, etc.)
78
Follow up and Monitoring Rx- Vitamin D
○ Safe in pregnancy if at recommended lower doses ■ Teratogenicity if taken at high doses ○ Safe in Lactation ○ Monitor creatinine/BUN, Calcium, Phosphate
79
Important determinants of serum Phosphorus levels
Renal excretion and intestinal absorption
80
Hyperphosphatemia cause
Advanced chronic kidney disease with decreased renal phosphate excretion is by far the most common cause
81
Treatment of Hyperphosphatemia is two fold
■ Optimize Tx of kidney disease ■ Consider treating with Phosphate binders ○ Dialysis can improve serum hyperphosphatemia
82
Hypophosphatemia causes
Can be caused by dozens of deranged metabolic processes ■ Ex: Meds, Diabetes, poor absorption, renal problems
83
Severe hypophosphatemia can lead to ____
tissue hypoxia and even rhabdomyolysis
84
Rx- Phosphorus MOA
Phosphorus replacement
85
Contraindications of Rx - Phosphorus
○ Hypoparathyroidism ○ Advanced chronic kidney disease
86
Adverse Reactions of Rx - Phosphorus
Hyperphosphatemia
87
Follow up and Monitoring for Rx - Phosphorus
Monitor serum phosphate and calcium levels closely, especially if administering via IV
88
Hypermagnesemia cause
○ Typically due to advanced CKD with impaired renal excretion. ○ May be secondary to Magnesium replacement or pregnant women treated for Preeclampsia/Eclampsia
89
High Mg 2+ characteristically results in____
muscle weakness, mental obtundation, and confusion
90
___ is usually necessary to remove Magnesium in those with severe kidney disease
Hemodialysis
91
Most common causes of Hypomagnesemia
Diuretics, Diarrhea, Alcoholism
92
Low Magnesium causes inhibition of ___ release
PTH
93
Rx- Magnesium MOA
Magnesium replacement/supplementation
94
Rx- Magnesium Indications
○ Low Magnesium (PO for mild, IV for symptomatic) ○ IV- Torsades de pointes, Preeclampsia/Eclampsia seizures
95
Contraindications of Rx - Magnesium
○ PO version- Ulcerative colitis, diverticulitis, colostomy ○ IV version- Myocardial damage, heart block
96
Side Effects of Rx - Magnesium
○ PO version- Nausea, vomiting, diarrhea ○ IV version- Drowsiness, diaphoresis, flushing
97
Adverse Reactions of Rx - Magnesium
○ PO version- None reported ○ IV version- Cardiac depression, Pulmonary edema
98
Follow up and Monitoring of Rx- Magnesium
○ 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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