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Parathyroid Flashcards

1
Q

How many parathyroid glands are there?

A

Usually 4

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2
Q

What percentage of patients have 5 parathyroid glands?

A

5%

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3
Q

What percentage of patients have 3 parathyroid glands?

A

10%

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4
Q

What is the usual position of the inferior parathyroid glands?

A

Posterior and lateral behind the thyroid and below the inferior thyroid artery

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5
Q

What is the most common site of an extra parathyroid gland?

A

Thymus gland

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6
Q

What percentage of patients have a parathyroid gland in the mediastinum?

A

1%

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7
Q

If only 3 parathyroid glands are found at surgery, where can the 4th one be hiding?

A

Thyroid gland, thymus, mediastinum, carotid sheath, tracheoesophageal groove, behind the esophagus

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8
Q

What is the embryologic origin of the superior parathyroid glands?

A

4th pharyngeal pouch

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9
Q

What is the embryologic origin of the inferior parathyroid glands?

A

3rd pharyngeal pouch

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10
Q

What supplies blood to the parathyroid glands?

A

Inferior thyroid artery

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11
Q

What percentage of patients have all 4 parathyroid glands supplied by the inferior thyroid arteries exclusively?

A

80%

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12
Q

What is DiGeorge’s syndrome?

A

Congenital absence of the parathyroid glands and the thymus

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13
Q

What is the most common cause of hypercalcemia in hospitalized patients?

A

Cancer

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14
Q

What is the most common cause of hypercalcemia in outpatients?

A

Hyperparathyroidism

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15
Q

What cell type produces PTH?

A

Chief cells

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16
Q

What are the major actions of PTH?

A

Increases blood calcium levels (takes from bone breakdown, GI absorption, increased resorption from kidney, excretion of phosphate by kidney)
Decreases serum phosphate

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17
Q

How does vitamin D work?

A

Increases intestinal absorption of calcium and phosphate

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18
Q

Where is calcium absorbed?

A

Duodenum and proximal jejunum

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19
Q

What is primary HPTH?

A

Increased secretion of PTH by parathyroid glands.

Marked by elevated calcium, low phosphate.

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20
Q

What is secondary HPTH?

A

Increased serum PTH resulting from calcium wasting cause by renal failure or decreased GI calcium absorption, rickets or osteomalacia.
Calcium levels are usually low.

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21
Q

What is tertiary HPTH?

A

Persistent HPTH after correction of secondary HPTH.

Results from autonomous PTH secretion not responsive to the normal negative feedback due to elevated Ca levels.

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22
Q

What are the methods of imaging the parathyroid glands?

A

Surgical operation, U/S, Sestamibi scan, TI-201 (technetium)-thallium subtraction scan, CT, MRI, A-gram, venous sampling for PTH

23
Q

What are the indications for a localizing preoperative study of the parathyroid glands?

A

Reoperation for recurrent HPTH

24
Q

What is the most common cause of primary HPTH?

A

Adenoma

25
Q

What are the etiologies of primary HPTH and percentages?

A

Adenoma (85%), hyperplasia (10%), carcinoma (1%)

26
Q

What is the incidence of primary HPTH in the US?

A

1-4/4000

27
Q

What are the risk factors for primary HPTH?

A

Family history, MEN-I and MEN-IIa, irradiation

28
Q

What are the signs and symptoms of primary HPTH hypercalcemia?

A

Stones (kidney stones);
Bones (bone pain, pathologic fractures, subperiosteal resorption);
Groans (muscle pain and weakness, pancreatitis, gout, constipation);
Psychiatric overtones (depression, anorexia, anxiety)
Also: polydipsia, weight loss, HTN, polyuria, lethargy

29
Q

What is the “33 to 1” rule?

A

Most patients with primary HPTH have a ratio of serum chloride to phosphate > 33

30
Q

What plain x-ray findings are classic for HPTH?

A

Subperiosteal bone resorption (usually in hand digits)

31
Q

How is primary HPTH diagnosed?

A

Labs (elevated PTH, hypercalcemia, hypophosphatemia, hyperchloremia).
Urine calcium should be checked for familial hypocalciuric hypercalcemia.

32
Q

What is familial hypocalciuric hypercalcemia?

A

AD inheritance of a condition of asymptomatic hypercalcemia and low urine calcium, with or without elevated PTH.
In contrast, hypercalcemia from HPTH results in high levels of urine calcium.

33
Q

What percentage of parathyroid adenomas are not single but found in more than one gland?

A

5%

34
Q

What is the initial medical treatment of primary HPTH hypercalcemia?

A

IV fluids, furosemide

35
Q

What is the definitive treatment of primary HPTH resulting from hyperplasia?

A

Neck exploration removing all parathyroid glands and leaving at least 30 mg of parathyroid tissue placed in the forearm muscles

36
Q

What is the definitive treatment of primary HPTH resulting from parathyroid adenoma?

A

Surgically remove adenoma (send for frozen section) and biopsy all abnormally enlarged parathyroid glands (some experts biopsy all glands)

37
Q

What is the definitive treatment of primary HPTH resulting from parathyroid carcinoma?

A

Remove carcinoma, ipsilateral thyroid lobe, and all enlarged lymph nodes (modified radical neck dissection for LN metastases)

38
Q

What is the definitive treatment of secondary HPTH?

A

Correct calcium and phosphate.

Perform renal transplantation (no role for parathyroid surgery)

39
Q

What is the definitive treatment of tertiary HPTH?

A

Correct calcium and phosphate.
Perform surgical operation to remove all parathyroid glands and reimplant 30-40 mg in the forearm if refractory to medical treatment.

40
Q

Why place 30-40 mg of sliced parathyroid gland in the forearm?

A

To retain parathyroid function.

If HPTH recurs, remove some of the parathyroid gland from the easily accessible forearm.

41
Q

What must be ruled out in the patient with HPTH from hyperplasia?

A

MEN-I and MEN-IIa

42
Q

What carcinomas are commonly associated with hypercalcemia?

A

Breast cancer metastases, prostate cancer, kidney cancer, liver cancer, pancreatic cancer, multiple myeloma

43
Q

What is the most likely diagnosis if a patient has a palpable neck mass, hypercalcemia, and elevated PTH?

A

Parathyroid carcinoma (vast majority of other causes of primary HPTH have non-palpable parathyroids)

44
Q

What is parathyroid carcinoma?

A

Primary carcinoma of the parathyroid gland

45
Q

What is the usual number of glands affected in parathyroid carcinoma?

A

1

46
Q

What are the signs and symptoms of parathyroid carcinoma?

A

Hypercalcemia, elevated PTH, palpable parathyroid gland, pain in neck, recurrent laryngeal nerve paralysis (change in voice), hypercalcemic crisis

47
Q

What is the common tumor marker for parathyroid carcinoma?

A

HCG

48
Q

What is the treatment for parathyroid carcinoma?

A

Surgical resection of parathyroid mass with ipsilateral thyroid lobectomy, ipsilateral lymph node resection

49
Q

What percentage of primary HPTH are caused by parathyroid carcinoma?

A

1%

50
Q

What are the possible postoperative complications after a parathyroidectomy?

A

Recurrent nerve injury (unilateral: voice change, bilateral: airway obstruction); neck hematoma (open at bedside if breathing is compromised); hypocalcemia; superior laryngeal nerve injury

51
Q

What is hungry bone syndrome?

A

Severe hypocalcemia seen after surgical correction of HPTH as chronically calcium-deprived bone aggressively absorbs calcium

52
Q

What is the treatment of hypoparathyroidism?

A

Acute: IV calcium
Chronic: PO calcium, vitamin D

53
Q

What is parathyromatosis?

A

Multiple small hyperfunctioning parathyroid tissue masses found over the neck and mediastinum.
Thought to be from congenital rests or spillage during surgery.

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