Parathyroid Flashcards
position of superior parathyroid in relation to RLN
posterior and lateral to RLN
position of inferior parathyroid in relation to RLN
anterior and medial
embryologic origin of superior parathyroids
4th pharyngeal pouch
embryologic origin of inferior parathyroids
3rd pharyngeal pouch
are the superior or inferior parathyroids more variable in location?
inferior
what cells release PTH? in response to what electrolyte derrangement?
the chief cells secrete PTH in response to low Ca
what cells release calcitonin and what is the stimulus?
parafollicular c-cells in response to high Ca
PTH effect on bone and kidney
bone - osteoclasts increase Ca and Phosphate reabsorption
kidneys - Ca reabsorption, inhibits phos and bicarb resorption (PHOS TRASHING HORMONE)
how does vit D increase serum Ca
increased Ca and phos absorption in gut
how does calcitonin decrease serum Ca in the bone and kidney?
bone - inhibits osteoclast bone resorption
Kidney - inhibits Ca and phos resorption
MCC cause of hypercalcemia in the outpatient setting? inpatient?
outpatient - primary hyperparathyroidism
inpatient - cancer
mechanism of hypercalcemia due to malignancy?
production of PTHrP
Tx for hypercalcemic crisis
hydration and loop diuretics. avoid LR (Ca)
MCC of primary hyperparathyroidism?
#1 adenoma #2 hyperplasia #3 parathyroid cancer (men 1 and 2A)
Lab pattern for hyperparathyroidism?
- increased Ca (24 hr collection), decreased phos (except renal failure)
- elevation of PTH
- Cl:Phos >33:1
- hypercalcuria, increased urinary cAMP
Best study to localize parathyroid adenoma?
sestamibi with SPECT + US
invasive study for adenoma localization?
angiography with venous sampling for PTH
Tx for hyperparathyroidism?
parathyroidectomy
SYMPTOMATIC PATIENTS SHOULD UNDERGO SURGERY
Tx for asymptomatic pt with hyperparathyroidism (5 instances)?
- Ca elevation >1mg/dL over normal value
- decreased Cr Clearance (<60 mL/min)
- T score
How do you confirm adequate resection of parathyroid adenoma?
need a >50% drop from baseline
treatment of multiglandular parathyroid disease
subtotal parathyroidectomy (3.5 glands)
OR
Total thyroidectomy with SCM or brachioradialis reimplantation
Who gets secondary hyperparathyroidism?
Renal failure patients
Tx of secondary hyperparathyroidism?
Ca/VitD supplementation, renal diet, phos binders
who gets tertiary hyperparathyroidism?
renal transplant patients who continue to have high PTH
Tx of tertiary hyperparathyroidism
subtotal parathyroidectomy or subtotal with parathyroid autotransplantation
Tx for parathyroid cancer
En bloc resection with ipsilateral thyroid and central neck dissection
chemorads is rarely effective
metabolic derangement in hyperparathyroidism
hyperchloremic metabolic acidosis, hypophos
bicarb is excreted due to PTH
elevated PTH, hypercalcemia, low urine Ca. what is Dx and Tx?
Dx - familial hypocalciuric hypercalcemia
Tx - nothing
does inferior thyroid artery supply the parathyroid laterally or medially?
medially
Where do you look for missing superior parathyroid gland?
retroesophageal space and open the carotid sheath
where do you look for missing inferior parathyroid gland?
ipsilateral mediastinal thymus OR intrathyroid gland
if four glands appear normal intraoperatively, but patient has elevated PTH - where do you look next?
thymus - hypersecreting supernumerary parathyroid gland
MC location of missed gland?
in NORMAL anatomic position
MC location of ectopic gland?
thymus
