23 Parathyroid Flashcards
Superior parathyroids
4th pharyngeal POUCH
Lateral to RLN, posterior to superior portion of the gland, above inferior thyroid artery
Inferior parathryoids
3rd pharyngeal POUCH
Medial to RLN, more anterior, below inferior thyroid artery
More likely to be ectopic
Most common ectopic site for parathryoid tissue?
Tail of the thymus
Anterior mediastinum, intra-thyroid, near tracehoesophageal groove
Blood supply to parathyroid glands?
All from inferior thyroid artery
Effect of PTH
Increases serum Ca
Increased kidney reabsorption in DCT, decreases PO4
Increased osteoclasts (increase Ca and PO4)
Increased vitamin D production in kidney
Increased Ca-binding protein in intestine
Effect of vitamin D
Increase intestinal Ca and PO4 resportion
Effect of calcitonin
Decreases serum Ca
Osteoclast inhibition
Increased urinary Ca and PO4 excretion
MCC hypoparathyroidism
Previous thyroid surgery
Primary hyperparathyroidsim
Increased Ca, decreased PO4, Cl to PO4 ratio > 33 Increased renal cAMP HCO3 secreted in uring Hyperchloremic metabolic acidosis Sx: muscle weakness, myalgia, nephrolithiasis, pancreatitis, PUD, depression, bone pain, pathologic fracture, mental status changes, constipation, anorexia, HTN
Work up for primary hyperparathyroidism
Test calcium levels (2-3 times)
CXR (mets, sarcoid, pulmonary tumors)
Excretory urogram (nephrlithiasis, renal tumor)
Serum protein electrophoresis (multiple myeloma)
24-hr calcium (benign famililal hypocalciuric hypercalemia)
R/O MEN
Check PTH level
Indications for surgery in hyperparathyroidism
Symptomatic disease Asymptomatic disease: - Ca >13 - Decreased Cr clearance - Kidney stones - Substantial decreased bone mass
Hyperparathyroidism treatment - adenoma
Resection
Inspect other glands to R/O hyperplasia or multiple adenoma
Hyperparathyroidism treatment - parathyroid hyperplasia
DO NOT biopsy all glands (risk of hemorrhage and hypo)
Resect 3 1/2 glands or total parathyroidectomy and autoinmplantation
Hyperparathyroidism treatment - parathyroid CA
Radical parathryoidectomy (take ipsilateral thryoid lobe)
Hyperparathyroidism treatment - pregnancy
Surgery in second trimester
Increased risk of stillbirth if not resected
Benefit of intra-op frozen sections in parathyroid surgery?
Confirm that tissue is parathyroid
Benefit of intra-op PTH levels?
Determined if causative gland is removed
PTH should drop to 1/2 pre-op value within 10 minutes
What to do if you cannot find parathyroid gland intra-op?
Check thymus tissue - can remove thymus tail and recheck PTH levels
Check near carotids, vertebral body, superior to pharnyx and thyroid
Still cannot find - close
- Check PTH, if still high, get Sestamibi scan
Post-operative hypocalcemia after parathryoidectomy
Bone hunger - normal PTH, decreased HCO3
Aparathyroidsim - decreased PTH, normal HCO3
Most common cause of peristent hyperparathryoidism?
Missed adenoma remaining in neck
Most common cause of recurrent hyperparathyroidism?
Occurs after a period of hypo or normocalcemia
- New adenoma
- Tumor implants
- Recurrent parathyroid CA
Sestamibi scan
Preferential uptake for overactive parathyroid gland
Good for adenomas and ectopic tissue
Not good for 4-gland hyperplasia
Secondary hyperparathyroidism
Renal failure
Increased PTH in respond to low serum Ca
Ectopic calcification and osteoporosis
Tx:
- Ca supplementation, Vit D, control diet PO4, PO4-binding gel, decrease aluminum
- Surgery for bone pain, fractures or pruritis
Tertiary hyperparathyroidism
Corrected renal disease - autonomous PTH overproduction
Hyperplasia
Surgery
Familial hypercalcemic hypocalciuria
Increased serum Ca, decreased urine Ca
Defect in PTH receptor in DCT
DX: Ca 9-11, normal PTH, decreased urine Ca
Tx: nothing, NO surgery
Pseudohypoparathyroidism
Defect in PTH receptor in kidney - does not respond to PTH
Parathyroid cancer
Increased Ca, PTH and alkaline phosphatase
Mets - lung
Tx: wide en bloc excision and ipsilateral thyroidectomy
MEN I
MENIN gene
Parathyroid hyperplasia
Pancreatic islet cell tumors
Pituitary adenoma
MEN IIa
RET proto-oncogene
Parathyroid hyperplasia
Medullary CA of thyroid
Pheochromocytoma
MEN IIb
RET proto-oncogene Medullary CA of thyroid Pheochromocytoma Mucosal neuromas Marfan's habitus
Causes of hypercalcemia
Malignancy - Hematologic - lytic bone lesions - Nonhematologic - PThrP (SCLC, breast) Hyperparathyroidism Hyperthyroidism Familial hypercalcemic hypocalciuria Immobilization Granulomatous disease Excess Vit D Milk-alkali syndrome Thiazide diuretics
Mithramycin
Inhibits osteoclasts
Used with malignancy or failure of conventional treatment of hypercalcemia
AE: hematologic, liver, renal
Hypercalcemic crisis
Secondary to other surgery in patients with pre-existing hyperparathyroidism
Tx: Fluids (NS), Lasix
Breast cancer causing hypercalcemia?
Mets to bone cause release of PTHrP
Same with SCLC
NOT bone destruction
Increased urinary cAMP
Hematologic cancer causing hypercalcemia?
Bony destruction
Urinary cAMP is low
