Parathyroid Flashcards
how many parathyroids are there?
usually four
what is the usual position of the inferior parathyroid glands?
posterior and lateral behind the thyroid and below the inferior thyroid artery
what is the most common site of an ‘extra’ gland?
thymus
if only three parathyroid glands are found at surgery, where can the fourth be hiding?
thyroid gland thymus/mediastinum carotid sheath tracheoesophageal groove behind the esophagus
what is the embryologic origin of the superior parathyroid glands?
fourth pharyngeal pouch
what is the embryologic origin of the inferior parathyroid glands?
third pharyngeal pouch
what supplies blood to all four parathyroid glands?
inferior thyroid artery
what is the most common cause of hypercalcemia in outpatients?
hyperparathyroidism
what cell type produces PTH?
chief cells produce PTH
what are the major actions of PTH?
increases blood calcium levels
- takes from bone breakdown, GI absorption, increased resorption from kidney, excretion of phosphate by kidney
decreases serum phosphage
how does vitamin D work?
increases intestinal absorption of calcium and phosphate
where is calcium absorbed?
duodenum and proximal jejunum
define primary hyperparathyroidism?
increased secretion of PTH by parathyroid glands
- marked by elevated calcium, low phosphorus
define secondary hyperparathyroidism?
increases serum PTH resulting from calcium wasting caused by renal failure or decreased GI calcium absorption, rickets or osteomalacia
- calcium levels are usually low
define tertiary hyperparathyroidism?
persistant hyperparathyroidism after correction of secondary hyperparathyroidism
- results from autonomous PTH secretion not responsive to the normal negative feedback due to elevated Ca2+ levels
what are the methods of imaging the parathyroids?
surgical operation
ultrasound
sestamibi scan
CT scan
what are the indications for a localizing preoperative study?
reoperation for recurrent hyperparathyroidism
what its the most common cause of primary hyperparathyroidism?
adenoma
what are the risk factors for primary hyperparathyroidism?
family history
MEN-I and MEN-IIa
irradiation
what are the signs/symptoms of primary hyperparathyroidism?
“stones, bones, groans, and psychiatric overtones”
- stones: kidney stones
- bones: bone pain, pathologic fractures, subperiosteal resoprtion
- groans: muscle pain and weakness, pancreatitis, gout, constipation
- psychiatric overtones: depression, anorexia, anxiety
- other: polydipsia, weight loss, HTN, polyuria, lethargy
what is the 33-to-1 rule?
most patients with primary hyperparathyroidism have a ratio of serum Cl- to phosphate >= 33
what plain X-ray findings are classic for hyperparathyroidism?
subperiosteal bone resorption
- usually in hand digits
- said to be pathognomonic for hyperparathyroidism
how is primary hyperparathyroidism diagnosed?
labs
- elevated PTH, hypercalcemia, decreased phosphorus, increased chloride
- urine calcium should be checked for familial hypocalciruic hypercalcemia
what is familial hypocalciuric hypercalcemia?
familial (autosomal dominant) inheritance of a condition of asymptomatic hypercalcemia and low urine calcium, with or without elevated PTH
- in contrast, hypercalcemia from hyperparathyroidism results in high levels of urine calcium
- surgery to remove parathyroid glands is not indicated for this diagnosis
what is the differential diagnosis of hypercalcemia?
CHIMPANZEES
- Calcium overdose
- Hyperparathyroidism, Hyperthyroidism, Hypocalciuric Hyprecalcemia
- Immobility/Iatrogenic (thiazide diuretic)
- Metastasis/Milk alkali syndrome (rare)
- Paget’s disease (bone)
- Addison’s disease/acromegaly
- Neoplasm (colon, lung, breast, prostate, multiple myeloma)
- Zollinger-Ellison syndrome
- Excessive Vitamin D
- Excessive Vitamin A
- Sarcoid
what is the initial medical treatment of hypercalcemia (primary hyperparathyroidism)?
medical
- IV fluids, furosemide
- NOT thiazide diuretics
although most recommend surgery for asymptomatic primary hyperparathyroidism, when is it considered mandatory?
ROACH
- Renal insufficiency
- Osteoporosis
- Age <50
- Calcium >1mg/dL above upper limit of normal
- Hypercalciuria >400mg/d Ca2+ excretion
what is the definition treatment of primary hyperparathyroidism from HYPERPLASIA?
neck exploration removing all parathyroid glands and leaving at least 30mg of parathyroid tissue placed in the forearm muscles
what is the definitive treatment of primary hyperparathyroidism from parathyroid ADENOMA?
surgically remove adenoma (send for frozen section) and biopsy all abnormally enlarged parathyroid glands (some experts biopsy all glands)
what is the definitive treatment of primary hyperparathyroidism from parathyroid CARCINOMA?
remove carcinoma, ipsilateral thyroid lobe, and all enlarged lymph nodes (modified radical neck dissection for LN metastases)
what is the definitive treatment of secondary hyperparathyroidism?
correct calcium and phosphate
perform renal transplantation
what is the definitive treatment of tertiary hyperparathyroidism?
correct calcium and phosphage
perform surgical operation to remove all parathyroid glands and reimplant 30-40mg in the forearm if refractory to medical management
why place 30-40mg of sliced parathyroid gland into the forearm?
to retain parathyroid function
- if hyperparathyroidism recurs, remove some of the parathyroid gland from the easily accessible forearm
what must be ruled out in the patient with hyperparathyroidism from hyperplasia?
MEN-I and MEN-IIa
what carcinomas are commonly associated with hypercalcemia?
breast cancer metastases
prostate cancer, kidney cancer, lung cancer, pancreatic cancer, multiple myeloma
what is the most likely diagnosis if a patient has a palpable neck mass, hypercalcemia, and elevated PTH?
parathyroid carcinoma
- vast majority of other causes of primary hyperparathyroidism have non palpable parathyroids
what is parathyroid carcinoma?
primary carcinoma of the parathyroid gland
what is the number of glands usually affected in parathyroid carcinoma?
1
what are the signs/symptoms of parathyroid carcinoma?
hypercalcemia, elevated PTH, PALPABLE parathyroid gland, pain in neck, recurrent laryngeal nerve paralysis, hypercalcemic crisis
what is the common tumor marker for parathyroid carcinoma?
human chorionic gonadotropin (HCG)
what are the possible postoperative complications after a parathyroidectomy?
recurrent nerve injury - unilateral: voice change - bilateral: airway obstruction neck hematoma - open at bedside if breathing is compromised hypocalcemia superior laryngeal nerve injury
what is ‘hungry bone syndrome’?
severe hypocalcemia seen after surgical correction of hyperparathyroidism as chronically calcium-deprived bone aggressively absorbs calcium
what are the signs/symptoms of postoperative hypocalcemia
perioral tingling, paresthesia, +Chvostek’s sign, +Trousseau’s sign, +tetany
what is the treatment of hypoparathyroidism?
actue: IV calcium
chronic: PO calcium, and vitamin D
What is parathyromatosis?
multiple small hyper functioning parathyroid tissue masses found over the neck and mediastinum
- thought to be formed from congenital rests or spillage during surgery
- remove surgically
