23 Parathyroid

Question 1

Superior parathyroids

Answer 1

4th pharyngeal POUCH

Lateral to RLN, posterior to superior portion of the gland, above inferior thyroid artery

Question 2

Inferior parathryoids

Answer 2

3rd pharyngeal POUCH
Medial to RLN, more anterior, below inferior thyroid artery
More likely to be ectopic

Question 3

Most common ectopic site for parathryoid tissue?

Answer 3

Tail of the thymus

Anterior mediastinum, intra-thyroid, near tracehoesophageal groove

Question 4

Blood supply to parathyroid glands?

Answer 4

All from inferior thyroid artery

Question 5

Effect of PTH

Answer 5

Increases serum Ca
Increased kidney reabsorption in DCT, decreases PO4
Increased osteoclasts (increase Ca and PO4)
Increased vitamin D production in kidney
Increased Ca-binding protein in intestine

Question 6

Effect of vitamin D

Answer 6

Increase intestinal Ca and PO4 resportion

Question 7

Effect of calcitonin

Answer 7

Decreases serum Ca
Osteoclast inhibition
Increased urinary Ca and PO4 excretion

Question 8

MCC hypoparathyroidism

Answer 8

Previous thyroid surgery

Question 9

Primary hyperparathyroidsim

Answer 9

Increased Ca, decreased PO4, 
Cl to PO4 ratio > 33
Increased renal cAMP
HCO3 secreted in uring
Hyperchloremic metabolic acidosis
Sx: muscle weakness, myalgia, nephrolithiasis, pancreatitis, PUD, depression, bone pain, pathologic fracture, mental status changes, constipation, anorexia, HTN

Question 10

Work up for primary hyperparathyroidism

Answer 10

Test calcium levels (2-3 times)
CXR (mets, sarcoid, pulmonary tumors)
Excretory urogram (nephrlithiasis, renal tumor)
Serum protein electrophoresis (multiple myeloma)
24-hr calcium (benign famililal hypocalciuric hypercalemia)
R/O MEN
Check PTH level

Question 11

Indications for surgery in hyperparathyroidism

Answer 11

Symptomatic disease
Asymptomatic disease:
- Ca >13
- Decreased Cr clearance
- Kidney stones
- Substantial decreased bone mass

Question 12

Hyperparathyroidism treatment - adenoma

Answer 12

Resection

Inspect other glands to R/O hyperplasia or multiple adenoma

Question 13

Hyperparathyroidism treatment - parathyroid hyperplasia

Answer 13

DO NOT biopsy all glands (risk of hemorrhage and hypo)

Resect 3 1/2 glands or total parathyroidectomy and autoinmplantation

Question 14

Hyperparathyroidism treatment - parathyroid CA

Answer 14

Radical parathryoidectomy (take ipsilateral thryoid lobe)

Question 15

Hyperparathyroidism treatment - pregnancy

Answer 15

Surgery in second trimester

Increased risk of stillbirth if not resected

Question 16

Benefit of intra-op frozen sections in parathyroid surgery?

Answer 16

Confirm that tissue is parathyroid

Question 17

Benefit of intra-op PTH levels?

Answer 17

Determined if causative gland is removed

PTH should drop to 1/2 pre-op value within 10 minutes

Question 18

What to do if you cannot find parathyroid gland intra-op?

Answer 18

Check thymus tissue - can remove thymus tail and recheck PTH levels
Check near carotids, vertebral body, superior to pharnyx and thyroid

Still cannot find - close
- Check PTH, if still high, get Sestamibi scan

Question 19

Post-operative hypocalcemia after parathryoidectomy

Answer 19

Bone hunger - normal PTH, decreased HCO3

Aparathyroidsim - decreased PTH, normal HCO3

Question 20

Most common cause of peristent hyperparathryoidism?

Answer 20

Missed adenoma remaining in neck

Question 21

Most common cause of recurrent hyperparathyroidism?

Answer 21

Occurs after a period of hypo or normocalcemia

• New adenoma
• Tumor implants
• Recurrent parathyroid CA

Question 22

Sestamibi scan

Answer 22

Preferential uptake for overactive parathyroid gland
Good for adenomas and ectopic tissue
Not good for 4-gland hyperplasia

Question 23

Secondary hyperparathyroidism

Answer 23

Renal failure
Increased PTH in respond to low serum Ca
Ectopic calcification and osteoporosis
Tx:
- Ca supplementation, Vit D, control diet PO4, PO4-binding gel, decrease aluminum
- Surgery for bone pain, fractures or pruritis

Question 24

Tertiary hyperparathyroidism

Answer 24

Corrected renal disease - autonomous PTH overproduction
Hyperplasia
Surgery

Question 25

Familial hypercalcemic hypocalciuria

Answer 25

Increased serum Ca, decreased urine Ca
Defect in PTH receptor in DCT
DX: Ca 9-11, normal PTH, decreased urine Ca
Tx: nothing, NO surgery

Question 26

Pseudohypoparathyroidism

Answer 26

Defect in PTH receptor in kidney - does not respond to PTH

Question 27

Parathyroid cancer

Answer 27

Increased Ca, PTH and alkaline phosphatase
Mets - lung
Tx: wide en bloc excision and ipsilateral thyroidectomy

Question 28

MEN I

Answer 28

MENIN gene
Parathyroid hyperplasia
Pancreatic islet cell tumors
Pituitary adenoma

Question 29

MEN IIa

Answer 29

RET proto-oncogene
Parathyroid hyperplasia
Medullary CA of thyroid
Pheochromocytoma

Question 30

MEN IIb

Answer 30

RET proto-oncogene
Medullary CA of thyroid
Pheochromocytoma
Mucosal neuromas
Marfan's habitus

Question 31

Causes of hypercalcemia

Answer 31

Malignancy
- Hematologic - lytic bone lesions
- Nonhematologic - PThrP (SCLC, breast)
Hyperparathyroidism
Hyperthyroidism
Familial hypercalcemic hypocalciuria
Immobilization
Granulomatous disease
Excess Vit D
Milk-alkali syndrome
Thiazide diuretics

Question 32

Mithramycin

Answer 32

Inhibits osteoclasts
Used with malignancy or failure of conventional treatment of hypercalcemia
AE: hematologic, liver, renal

Question 33

Hypercalcemic crisis

Answer 33

Secondary to other surgery in patients with pre-existing hyperparathyroidism
Tx: Fluids (NS), Lasix

Question 34

Breast cancer causing hypercalcemia?

Answer 34

Mets to bone cause release of PTHrP
Same with SCLC
NOT bone destruction
Increased urinary cAMP

Question 35

Hematologic cancer causing hypercalcemia?

Answer 35

Bony destruction

Urinary cAMP is low