Parathyroid

Question 1

What is the embryologic origin of the parathyroid glands?

Answer 1

Superior glands develop from the fourth pharyngeal pouch, while inferior glands develop from the third pharyngeal pouch

Question 2

What is the average size of a parathyroid gland?

Answer 2

<50 mg and 3x3x3 mm

Question 3

What is the histologic appearance of a normal parathyroid gland?

Answer 3

Mainly chief cells, with occasional oxyphils

Question 4

Describe the vascular supply of the parathyroid glands?

Answer 4

Afferent supply from the inferior thyroid arteries; efferent drainage to the superior, middle, and inferior thyroid veins.

Question 5

To what does active, ionized serum calcium bind to under normal circumstances?

Answer 5

80% bound to albumin. 20% found in a citrate complex

Question 6

What is the primary function of the parathyroid gland

Answer 6

To regulate calcium and phosphate in conjunction with vitamin D and calcitonin

Question 7

What are the effects of PTH on bone?

Answer 7

1. Stimulate osteoclasts
2. Inhibit osteoblasts
3. Stimulates bone resorption, releasing calcium and phosphate

Question 8

What are the effects of PTH on the kidney?

Answer 8

1. Increases reabsorption of calcium

2. Increases phosphate excretion

Question 9

What are the effects of PTH on the GI tract?

Answer 9

Stimulates hydroxylation of 25-OH D

Question 10

Define hypercalcemic crisis and its treatment.

Answer 10

Serum calcium >13 mg/dL and symptomatic. Treat with saline, diuretics, and if needed anti-arrhythmic medication

Question 11

What is the role of Vit D as it relates to PTH?

Answer 11

Increased 1,25 OH D increases absorption of calcium and phosphate, promotes mineralization, and enhances PTH’s effect on bone

Question 12

What is the role of calcitonin?

Answer 12

Inhibits bone resorption, increases urinary excretion of calcium and phosphate.

Question 13

What cells produce calcitonin?

Answer 13

C-cells of the thyroid

Question 14

What are the biochemical effects of hyperparathyroidism?

Answer 14

1. Increased absorption of calcium from the intestines
2. Increase vitamin D3 production
3. Decreased renal calcium excretion

All three raise serum calcium levels

Question 15

What are the signs and symptoms of hyperparathyroidism?

Answer 15

Kidney stones, bone pain, pathologic fractures, nausea, vomiting, constipation, pancreatitis, peptic ulcer disease, lethary, confusion, depression, paranoia

Question 16

What are the common etiologies of hyperparathyroidism?

Answer 16

1. 85-90% are solitary adenomas
2. 10% are four-gland hyperplasia
3. <1% are cancers

Question 17

What are the pre-operative tests for localizing the cause of hyperparathyroidism?

Answer 17

US, FNA of suspicious US findings, Sestamibi scan

Question 18

What are the serum lab values typical of hyperparathyroidism?

Answer 18

elevated plasma PTH, with inappropriately high serum calcium

Question 19

What is the treatment for solitary adenomas causing hyperparathyroidism?

Answer 19

Solitary parathyroidectomy

Question 20

What is the treatment of multiple gland hyperplasia causing hyperparathyroidism?

Answer 20

Remove 3 glands, or all four glands with reimplantation of one gland in the forearm.

Question 21

What is the most common cause of hypercalcemia in the outpatient population? What about the inpatient population?

Answer 21

Outpatient: Hyperparathyroidism
Inpatient: Hypercalcemia of malignancy

Question 22

What is the success rate of surgical correction for hyperparathyroidism?

Answer 22

98% cure from first operative procedure.

90% cure from second procedure of remaining gland is well localized per-operatively

Question 23

What are common causes of secondary hyperparathyroidism?

Answer 23

1. Chronic renal failure

2. Intestinal malabsorption

Question 24

What is the treatment for patients with hyperparathyroidism as part of MEN syndrome?

Answer 24

Because of the high rate of recurrence, these patients require total parathyroidectomy with forearm reimplantation to facilitate potential reoperations.

Question 25

What are some of the signs and symptoms of secondary hyperparathyroidism?

Answer 25

Patients are often asymptomatic. | May present as bone pain from renal osteodystrophy and pruritus

Question 26

What are the treatments for hyperparathyroidism caused by chronic renal failure?

Answer 26

Nonsurgical: restrict phosphorus intake, give phosphorus-binding agents and calcium/vitamin D supplementation, adjust dialysate to maximize calcium and minimize aluminum. Surgical treatment is indicated for intractable bone pain or pruritus, or pathologic fractures in patients who have failed medical therapy.

Question 27

What is the surgical procedure of choice in patients with secondary hyperparathyroidism?

Answer 27

3.5 gland parathyroidectomy

Question 28

What is the cause of tertiary hyperparathyroidism?

Answer 28

Caused by autonomously functioning parathyroid glands, resistant to negative feedback, generally in the case of prolonged secondary hyperparathyroidism, which does not resolve once the primary cause has been address (for example, persistent hypercalcemia following renal transplantation)

Question 29

What is the treatment for tertiary hyperparathyroidism?

Answer 29

Generally, it is a short lived phenomenon. If persistent, surgical excision with 3.5 gland parathyroidectomy is indicated.

Question 30

What are the common etiology of hypoparathyroidism?

Answer 30

1. Iatrogenic 2/2 surgery - usually following total thyroidectomy; often transient and only treated if symptomatic 2. Congenital absence of all four parathyroid glands 3. DiGeorge Syndrome: Absence of parathyroids along with thymic agenesis 4. Functional: chronic hypomagnesemia

Question 31

What are the signs and symptoms of hypoparathyroidism?

Answer 31

1. Numbness and tingling of circumoral area, fingers, and toes 2. Anxiety and confusion 3. Late manifestations include tetany, hyperventilation, seizures, and heart block

Question 32

What is the treatment of hypoparathyroidism?

Answer 32

Supplementation with calcium and vitamin D

Question 33

What is pseudohypoparathyroidism, and how do you treat it?

Answer 33

An inherited disorder in which target tissues are resistant to PTH effects. Patients remain hypocalcemic and hyperphosphatemic despite bone resorption from elevated PTH. Treatment consists of calcium and vitamin D supplementation.

Question 34

What is Chvostek's sign, and what causes it?

Answer 34

Contraction of facial muscles when tapping on facial nerve. Caused by hypocalcemia

Question 35

What is Trousseau's sign, and what causes it?

Answer 35

Development of capal spasms by occluding blood flow to the forearm. Caused by hypocalcemia.

Question 36

What are the signs and symptoms of parathyroid cancer?

Answer 36

1. 40-50% present with firm, fixed mass. 2. Extremely high calcium, PTH, and alkaline phosphatase 3. Associated bone disease, renal insufficiency, and renal stones

Question 37

What are the gross and microscopic findings of parathyroid cancer?

Answer 37

Pale, while, adherent mass with a thick fibrous capsule and septations. Enlarged hyperchromatic nuclei and varied nuclear size.

Question 38

What is the treatment for parathyroid cancer?

Answer 38

1. En bloc surgical resection of the mass and surrounding structures, ipsilateral thyroid lobectomy, and regional lymph node dissection. 2. Postoperative radiation therapy and chemotherapy are NOT typically indicated

Question 39

What is the five year survival of parathyroid cancer?

Answer 39

70%