Endocrine: Parathyroid

Question 1

Where are parathyroid glands usually located?

Answer 1

Posterior to the thyroid (often in the tracheoesophageal groove)

Question 2

What embryological structure gives rise to the parathyroid glands?

Answer 2

• 4th branchial pouch (superior 2 glands)
• 3rd branchial pouch (inferior 2 glands)

Note: The inferior 2 glands are often in an ectopic location.

Question 3

What is the most common cause of hyperparathyroidism?

Answer 3

Parathyroid adenoma (90%)

Question 4

Hypercalcemia

Answer 4

Think parathyroid adenoma

Question 5

Hypercalcemia

Answer 5

Think parathyroid adenoma

Question 6

Answer 6

Think parathyroid adenoma

Note: Hypodense on non contrast, intense arterial enhancement, and washout on delayed images.

Question 7

What nuclear imaging tests can be used to evaluate for parathyroid adenoma?

Answer 7

• Single-tracer, dual-phase sestamibi
• Dual-tracer (sestamibi and I-123/pertechnetate)

Question 8

And cervical lymphadenopathy

Answer 8

Think parathyroid carcinoma

Note: Looks exactly like a parathyroid adenoma, but is associated with invasion or adjacent structures and/or cervical lymphadenopathy.

Question 9

Differential for hyperparathyroidism

Answer 9

• Hyperfunctioning parathyroid adenoma (90%)
• Multi-gland parathyroid hyperplasia (8-10%)
• Parathyroid cancer (1-3%)

Question 10

What factors does sestamibi parathyroid imaging depend on?

Answer 10

• Mitochondrial density
• Blood flow