Parathyroid Flashcards
The parathyroids receive their blood supply from where?
all four get their arterial inflow from the inferior thyroid artery
What is the embryologic origin of the parathyroids?
- superior from the fourth pharyngeal pouch
- inferior from the third
How are the parathyroids located relative to the RLN?
- superior are posterior and lateral to the nerve
- inferior and anterior and medial
What cells release parathyroid hormone? Calcitonin?
- PTH from chief cells
- calcitonin from c-cells of the thyroid
What are the effects of PTH?
- stimulates osteoclasts
- stimulates calcium resorption and phosphate secretion in the kidneys
- stimulates activation of vit D in the kidneys
How does vitamin D increase calcium?
by stimulating increased absorption of Ca and P from the GI tract
What are the most common causes of hypercalcemia in an inpatient and outpatient setting?
- inpatient: malignancy
- outpatient: primary hyperparathyroidism
Which lung cancer releases PTHrP?
squamous cell
How is hypercalcemic crisis treated?
- high volume of normal saline
- lasix
- bisphosphates
What is the most specific test for diagnosing hyperparathyroidism?
chloride/phosphate > 33
What are the indications of symptomatic patients with hyperparathyroidism to undergo parathyroidectomy?
- calcium > 1 above normal
- CrCl < 60
- poor access to care/follow up
- age < 50
What confirms adequate resection of a parathyroid adenoma?
more than 50% drop on intra-op rapid PTH assay
In which patients do you see tertiary hyperparathyroidism and how is this treated?
- usually in post-renal transplant patients
- due to long-term dysregulation of the feedback loop, triggering autonomous PTH production by parathyroids
- treated with subtotal parathyroidectomy
How is secondary hyperparathyroidism treated?
- calcium and vit D supplements
- phosphate binders
- renal diet
How is parathyroid carcinoma treated?
en bloc resection with ipsilateral thyroid and central neck dissection
What are the electrolyte disturbances seen with hyperparathyroidism?
- hyperchloremic metabolic acidosis
- hypophosphatemia
- hypercalcemia
How is benign familial hypocalciuric hypercalcemia treated?
NTD
How is benign familial hypocalciuric hypercalcemia diagnosed?
- high PTH
- high serum calcium
- low urine calcium
Where should you look for aberrant parathyroid glands?
- superior in the retroesophgeal space and within the carotid sheath
- inferior in the thymus or thyroid tissue
You find four normal parathyroids in someone with elevated PTH, what’s the next step?
consider hyper secreting supernumerary parathyroid gland, look in the thymus/thymectomy
What is the most common location of a missed parathyroid gland?
the normal anatomic position
What is the most common location of an ectopic parathyroid gland?
the thymus
