Parathyroid Flashcards
Are chemo and radiation beneficial for parathyroid carcinoma?
No
What do you do if you encounter a parathyroid carcinoma when doing a parathyroidectomy?
En bloc resection of the parathyroid gland and ipsilateral thyroid lobe along with regional lymph nodes.
Indications for parathyroidectomy?
1) Age < 50 y.o.
2) Ca > 1 mg/dl over normal
3) Urinary Ca > 400 mg/24 hours
4) Osteoporosis T score < -2.5
5) Compression fractures, nephrolithiasis
6) CrCl < 60
7) Poor followup
Indication for bilateral exploration for primary hyperparathyroidism?
Lithium exposure -> HPT; b/c there is an increased incidence in 4 gland hyperplasia compared to gen pop
Anatomy of superior parathyroid
Post/Lat to recurrent laryngeal nerve
From 4th pharyngeal pouch
Anatomy of inferior parathyroid
Ant/Med to recurrent laryngeal nerve
From 3rd pharyngeal pouch (just like the thymus)
More variable location
Blood supply to parathyroid glands
Inferior parathyroid artery (80%) - from thyrocervical trunk
Parathyroid function
Cheif cells - PTH in response to low Ca
Parafollicular C cells - Release calcitonin in response to high Ca (actually located in thyroid)
Vit D process
Ingested then hydroxylated @ 25 in the liver; hydroxylated @ 1 in the kidney -> now most active
Parathyroid hormone acts on?
2 sites:
Bone: Stimulates osteoclasts for resorption of Ca/P
Kidney: Stimulates resorption of Ca, inhibits resorption of P/HCO3
People with high PTH have very low P
Vit D affects
Stimulates absorption of Ca/P in gut
Stimulates absorption of Ca; and wasting of P in kidneys
Calcitonin affects
Bones: Inhibits osteoclasts
Kidney: Inhibits resorption of Ca/P
HyperCa presentation
1) on labs as high Ca
MC cause in outpatient setting- > primary hyperPTH
2) MC inpatient cause -> Cancer
Ex: Squamous cell cancer (pthrp), breast cancer
HyperCa crisis tx
1) Fluids - NS @ 300 cc/hr
2) When euvolemic add lasix
Primary hyperPTH
MC cause single adenoma
Other cause, hyperplasia of all glands, cancer, MEN 1, 2A
Lab workup of primary hyperPTH
High Ca on lab
Get 24 hour urine collection -> Inc Ca and Dec P except in renal failure inc both
HyperChloremic; large Cl:P ratio (33:1)
Blood effect of primary hyperPTH
High Ca, Dec P
Localization of adenoma
Non-invasive: US, sestamibi, SPECT, MRI
Best Sestamibi with SPECT +/- US
Invasive: Angiography with selective venous sampling for PTH gradients
HyperPTH Tx?
Parathyroidectomy
Intra-op confirmation of removal
50% drop of parathyroid level 10 mins post removal of adenoma
Multigland dz Tx:
1) Subtotal (3.5 glands) -> start with 0.5 gland resection
2) Total with reimplantation of 0.5 glands
Secondary hyperPTH
Pts with renal failure -> low Ca -> so inc PTH
Tx: Give Ca/Vit D supplements and phos binders
Tertirary hyperPTH
Have 2ndary PTH -> get renal txp -> still have hyperPTH
Tx: Subtotal parathyroidectomy
Parathyroid cancer; HyperCa from cancer
Ca>15 with possible mass
Tx: En bloc resection with ipsilateral thyroid, central neck dissection
Parathyroid cancer recurrence/no
Chemo/rads don’t work
Palliative surgery with Ca lowering drugs like bisphosphonates
High normal Ca, Elevated PTH, bone loss
Normocalcemic, hyperPTH -> primary hyperPTH; tx is resection
Symptoms of hyperCa
Bones, stones, psychiatric overtones
Electrolyte disturbances with hyperPTH
HyperCl met acidosis (Cl:P > 33:1)
HypoPhos; or elevated with renal impairment
HyperPTH, HyperCa, low Urinary Ca
Benign familial hypocalciuric hypercalcemia
Setpoint of PTH receptor is higher
Tx: Nothing
Inferior thyroid artery anatomical position to nerve
Artery is medial to the nerve
Important because you want to dissect lateral half of a gland if you are only dissection 0.5
MC location of a missed gland
In normal anatomic position
MC location of an ectopic gland
In the thymus
