Parathyroid

Question 1

Superior parathyroid glands

1) embryonic origin
2) location

Answer 1

1) 4th endodermal pharyngeal pouch
2) Posteromedial aspect of upper pole of thyroid, within 2cm of intersection of RLN and ITA, at level fo cricoid cartilage

Question 2

Superior parathyroid glands

1) embryonic origin
2) location

Answer 2

1) 4th branchial pouch
2) posteromedial aspect of upper pole of thyroid, within 2cm of intersection of RLN and ITA, at level fo cricoid cartilage

Question 3

Inferior parathyroid glands

1) embryonic origin
2) location

Answer 3

1) 3rd endodermal pharyngeal pouch
2) more variable
posterolateral aspect of lower pole, below intersection of RLN and ITA

Question 4

Indications for parathyroidectomy in asymptomatic patients with hyperparathyroidism

Answer 4

1) Age<50
2) Adjusted calcium >0,25 mmol above upper limit
3) CrCl reduced by more than 30%
4) 24 hr total urinary calcium excretion >10mmol
5) Bone mineral density T score -2.5 or less
6) Patient request

Question 5

Complications of Parathyroidectomy

Answer 5

RLN injury
Bleeding
Airway obstruction
Hungry bone syndrome
(hypocalcemia, hyponatremia, hypomagnesium)

Question 6

Possible locations of P4

Answer 6

• Behind superior pole of thyroid (most common)
• Carotid bifurcation
• Subcapsular/intrathyroidal
• Retroesophageal area

Question 7

Possible location of P3

Answer 7

• Thymus
• Carotid bifurcation
• Subcapsular/intrathyroidal
• Retroesophageal area
• Mediastinal

Question 8

What are the actions of PTH?

Answer 8

Aims for elevation of calcium in bloodstream

• bone resorption via PTH receptors acting on osteoclasts
• increase production of 1,25-DHCC by kidney (to increase resorption of calcium from gut) , increase excretion of phosphate

Question 9

What hormones are involved in calcium homeostasis?

Answer 9

• PTH
• 1,25 DiHydroxyCholeCalciferol
• Calcitonin

Question 10

What are the action of 1, 25 DiHydroxyCholeCalciferol?

Question 11

How to prevent hypoparathyroidism?

Answer 11

• Treat every parathyroid gland as if the last
• Never perform truncal ligation of inferior thyroid artery - lateral thermal spread could impair blood supply to parathyroid
• Rational use of energy platform
• Understand anatomy of parathyroid
• Always perform auto-transplantation if parathyroid devascularized

Question 12

When do you offer parathyroidectomy

Answer 12

• Symptomatic hypercalcemia
• Asymptomatic hypercalcemia when
  
  • Calcium >2.8mmol/L or 0.25mmol above UL
  • Skeletal involvement: DEXA scan ←2.5 in LS spine, total hip, femoral neck or distal radius
  • Renal involvement:
    
    • CrCl< 60ml/min
    • 24 hour urine calcium> 10mmol/day
    • Nephrolithiasis

Question 13

What does an abnormal parathyroid gland look like?

Answer 13

• Reddish brown color (increase mitochondria)
• Spherical shape
• Firm
• Enlarged (>40mg)

Question 14

How to perform bilateral neck exploration

Answer 14

• Collar incision
• Develop subplatsymal flaps
• Dissection along midline raphe
• Locate all 4 parathyroid glands
• If only one abnormal, treat as single adenoma and excise

Question 15

What to do if all four parathyroids normal or abnormal?

Answer 15

• Find most normal, excise half for frozen section
  
  • if cellular parathyroid (abnormal), then four gland hyperplasia, excise other 3, leave half or most normal in-situ/ autotransplant
  • if normal, find second most normal and excise half →
    
    • if cellular, excise other 2 glands
    • if normal, proceed to third most normal