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Embryologic origin of superior parathyroids
4th pharyngeal pouch
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Location of superior parathyroids
Lateral to RLNs, above inferior thyroid artery
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Embryologic origin of inferior parathyroids
3rd pharyngeal pouch
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Location of inferior parathyroids
Medial to RLNs, below inferior thyroid artery
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Most common ectopic site for parathyroids
Tail of thymus
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Ectopic sites for parathyroids (4)
Tail of thymus, intrathyroid, posterior mediastinal, near tracheoesophageal groove
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Blood supply to all parathyroid glands
Inferior thyroid artery
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Role of PTH
Increase serum Ca, increase Ca release from bone, increase Vit D production in kidney
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Role of Vitamin D in Calcium and phosphorus
Increase intestinal absorption by increasing calcium binding protein
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Role of calcitonin
Decrease serum Ca, decrease bone resorption of Ca, increase urinary Ca and Phos excretion
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Normal calcium level
8.5-10.5
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Normal ionized calcium level
4.4-5.5
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Most common cause of hypoparathyroidism
Previous thyroid surgery
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Oncogene that increases risk of parathyroid adenomas
PRAD-1
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Lab values in primary hyperparathyroidism (Ca, Phos, Cl)
Inc calcium, dec phos, Cl:Phos ratio >33
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Metabolic derangement seen in primary hyperparathyroidism
Hyperchloremic metabolic acidosis
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Bone lesions from calcium resorption seen in hyperparathyroidism
Osteitis fibrosa cystica
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Symptoms of hyperparathyroidism (4)
Stones (nephrolithiasis), bones (bone pain, patholological fractures, muscle weakness, myalgia), groans (pancreatitis, PUD, constipation, nausea, vomiting), psychiatric overtones (mental status changes, depression)
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Indications for parathyroidectomy in primary hyperparathyroidism
Symptomatic disease, Ca >13, dec creatinine clearance, substantially dec bone mass
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Most common cause of primary hyperparathyroidism
Single adenoma
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Causes of primary hyperparathyroidism (3)
Adenomas (multiple or single), diffuse hyperplasia, parathyroid adenocarcinoma
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Treatment of parathyroid hyperplasia
Resect 3 � glands, or total resection + auto-implant
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Half-life of PTH
18 minutes
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Most common position of missing gland (at reoperation)
Normal anatomic position
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Diagnostic imaging to localize parathyroids (2)
Thallium-technetium scan, Sestamibi-iodine scan
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Increased PTH in response to low Ca, seen in patients with renal failure
Secondary hyperparathyroidism
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Aluminum accumulation in bones after several years of hemodialysis
Renal osteodystrophy
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Indications for surgery in secondary parathyroidism
Bone pain, fractures, pruritis
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Increased PTH despite corrected renal disease
Tertiary hyperparathyroidism
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Defect in PTH receptor in kidney causing increased resorption of Ca
Familial hypercalcemic hypocalciuria
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Defect in PTH receptor in kidney which causes a lack of response to PTH
Pseudohyperparathyroidism
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Most common location of parathyroid cancer mets
Lung
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Treatment of parathyroid cancer
Parathyroidectomy and ipsilateral thyroidectomy
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Mortality cause of parathyroid cancer
Hypercalcemia
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Tumors seen in MEN1 (3)
Parathyroid hyperplasia, pancreatic islet cell tumors, pituitary adenoma
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First part to become symptomatic in MEN1
Parathyroid
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Most common pancreatic islet cell tumor in MEN1
Gastrinoma
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Tumors seen in MEN2a (3)
Pheo, parathyroid hyperplasia, MTC
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Most common symptom of MTC in MEN2a and 2b
Diarrhea
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#1 cause of death in MEN2a and 2b
MTC
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First part to become symptomatic in MEN2a
MTC
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Tumors seen in MEN2b
Pheochromocytoma, MTC, mucosal neuromas
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Gene implicated in MEN1
MENIN
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Gene implicated in MEN2a and 2b
RET
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Causes of hypercalcemia (11)
Calcium administration, hyperparathyroidism, immobility/iatrogenic, milk-alkali syndrome, Paget�s disease, Addison�s disease, neoplasm, thiaZide diuretics, excess vit D, excess Vit A, sarcoid/TB
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Drug used in malignancies after failed conventional treatment; inhibits osteoclasts
Methramycin
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Hormone released by breast cancer bone mets and SCLC causing hypercalcemia
PTHrp
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