Parathyroid C59 P452-458 Flashcards
ANATOMY
How many parathyroids are
there?
P452
Usually four (two superior and two inferior)
ANATOMY
What percentage of patients
have five parathyroid glands?
P452
≈5% (Think: 5 = 5)
ANATOMY What percentage of patients have three parathyroid glands? P452
≈10%
ANATOMY What is the usual position of the inferior parathyroid glands? P452
Posterior and lateral behind the thyroid
and below the inferior thyroid artery
ANATOMY
What is the most common
site of an “extra” gland?
P452
Thymus gland
ANATOMY What percentage of patients have a parathyroid gland in the mediastinum? P452
≈1%
ANATOMY If only three parathyroid glands are found at surgery, where can the fourth one be hiding? P452
Thyroid gland Thymus/mediastinum Carotid sheath Tracheoesophageal groove Behind the esophagus
ANATOMY What is the embryologic origin of the following structures: Superior parathyroid glands? P453
Fourth pharyngeal pouch
ANATOMY What is the embryologic origin of the following structures: Inferior parathyroid glands? P453
Third pharyngeal pouch
counterintuitive
ANATOMY
What supplies blood to the
parathyroid glands?
P453
Inferior thyroid artery
ANATOMY What percentage of patients have all four parathyroid glands supplied by the inferior thyroid arteries exclusively? P453
≈80%
ANATOMY
What is DiGeorge’s
syndrome?
P453
Congenital absence of the parathyroid
glands and the thymus
ANATOMY What is the most common cause of hypercalcemia in hospitalized patients? P453
Cancer
ANATOMY What is the most common cause of hypercalcemia in outpatients? P453
Hyperparathyroidism
PHYSIOLOGY
What cell type produces
PTH?
P453
Chief cells produce ParaThyroid
Hormone (PTH)
PHYSIOLOGY
What are the major actions
of PTH?
P453
Increases blood calcium levels (takes from bone breakdown, GI absorption, increased resorption from kidney, excretion of phosphate by kidney), decreases serum phosphate
PHYSIOLOGY
How does vitamin D work?
P453
Increases intestinal absorption of calcium
and phosphate
PHYSIOLOGY
Where is calcium absorbed?
P453
Duodenum and proximal jejunum
HYPERPARATHYROIDISM (HPTH)
Define primary HPTH.
P454
Increased secretion of PTH by parathyroid
gland(s); marked by elevated calcium,
low phosphorus
HYPERPARATHYROIDISM (HPTH)
Define secondary HPTH.
P454
Increased serum PTH resulting from calcium wasting caused by renal failure or decreased GI calcium absorption, rickets or osteomalacia; calcium levels are usually low
HYPERPARATHYROIDISM (HPTH)
Define tertiary HPTH.
P454
Persistent HPTH after correction of secondary hyperparathyroidism; results from autonomous PTH secretion not responsive to the normal negative feedback due to elevated Ca⁺ ⁺ levels
HYPERPARATHYROIDISM (HPTH)
What are the methods of
imaging the parathyroids?
P454
Surgical operation
Ultrasound
Sestamibi scan
201TI (technetium)–thallium subtraction
scan
CT/MRI
A-gram (rare)
Venous sampling for PTH (rare)HYPERPARATHYROIDISM (HPTH) What are the indications for a localizing preoperative study? P454
Reoperation for recurrent
hyperparathyroidism
HYPERPARATHYROIDISM (HPTH)
What is the most common
cause of primary HPTH?
P454
Adenoma ( >85%)
HYPERPARATHYROIDISM (HPTH) What are the etiologies of primary HPTH and percentages? P454
Adenoma ( ≈85%)
Hyperplasia ( ≈10%)
Carcinoma ( ≈1%)
HYPERPARATHYROIDISM (HPTH) What is the incidence of primary HPTH in the United States? P454
≈1/1000–4000
HYPERPARATHYROIDISM (HPTH)
What are the risk factors for
primary HPTH?
P454
Family history, MEN-I and MEN-IIa,
irradiation
HYPERPARATHYROIDISM (HPTH) What are the signs/ symptoms of primary HPTH hypercalcemia? P455
“Stones, bones, groans, and
psychiatric overtones”:
Stones: Kidney stones
Bones: Bone pain, pathologic
fractures, subperiosteal resorption
Groans: Muscle pain and weakness,
pancreatitis, gout, constipation
Psychiatric overtones: Depression,
anorexia, anxiety
Other symptoms: Polydipsia, weight
loss, HTN (10%), polyuria, lethargyHYPERPARATHYROIDISM (HPTH)
What is the “33 to 1” rule?
P455
Most patients with primary HPTH have a
ratio of serum (Cl⁻) to phosphate ≥33
HYPERPARATHYROIDISM (HPTH)
What plain x-ray findings are
classic for HPTH?
P455
Subperiosteal bone resorption (usually in
hand digits; said to be “pathognomonic”
for HPTH!)
HYPERPARATHYROIDISM (HPTH)
How is primary HPTH
diagnosed?
P455
Labs—elevated PTH (hypercalcemia,
↓ phosphorus, ↑ chloride); urine calcium
should be checked for familial
hypocalciuric hypercalcemia
HYPERPARATHYROIDISM (HPTH)
What is familial hypocalciuric
hypercalcemia?
P455
Familial (autosomal-dominant)
inheritance of a condition of
asymptomatic hypercalcemia
and low urine calcium, with or
without elevated PTH; in contrast,
hypercalcemia from HPTH results in
high levels of urine calcium
Note: Surgery to remove parathyroid
glands is not indicated for this diagnosisHYPERPARATHYROIDISM (HPTH) How many of the glands are USUALLY affected by the following conditions: Hyperplasia? P455
4
HYPERPARATHYROIDISM (HPTH) How many of the glands are USUALLY affected by the following conditions: Adenoma? P455
1
HYPERPARATHYROIDISM (HPTH) How many of the glands are USUALLY affected by the following conditions: Carcinoma? P455
1
HYPERPARATHYROIDISM (HPTH) What percentage of adenomas are not single but found in more than one gland? P455
≈5%
HYPERPARATHYROIDISM (HPTH)
What is the differential
diagnosis of hypercalcemia?
P456
“CHIMPANZEES”:
Calcium overdose
Hyperparathyroidism (1/2/3),
Hyperthyroidism, Hypocalciuric
Hypercalcemia (familial)
Immobility/Iatrogenic (thiazide
diuretics)
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
SarcoidHYPERPARATHYROIDISM (HPTH) What is the initial medical treatment of hypercalcemia (1 HPTH)? P456
Medical—IV fluids, furosemide—NOT
thiazide diuretics
HYPERPARATHYROIDISM (HPTH) What is the definitive treatment of HPTH in the following cases: Primary HPTH resulting from HYPERPLASIA? P456
Neck exploration removing all parathyroid glands and leaving at least 30 mg of parathyroid tissue placed in the forearm muscles (nondominant arm, of course!)
HYPERPARATHYROIDISM (HPTH) What is the definitive treatment of HPTH in the following cases: Primary HPTH resulting from parathyroid ADENOMA? P456
Surgically remove adenoma (send for
frozen section) and biopsy all abnormally
enlarged parathyroid glands (some
experts biopsy all glands)
HYPERPARATHYROIDISM (HPTH) What is the definitive treatment of HPTH in the following cases: Primary HPTH resulting from parathyroid CARCINOMA? P456
Remove carcinoma, ipsilateral thyroid
lobe, and all enlarged lymph nodes
(modified radical neck dissection for LN
metastases)
HYPERPARATHYROIDISM (HPTH) What is the definitive treatment of HPTH in the following cases: Secondary HPTH? P456
Correct calcium and phosphate; perform
renal transplantation (no role for
parathyroid surgery)
HYPERPARATHYROIDISM (HPTH)
Tertiary HPTH?
P457
Correct calcium and phosphate; perform surgical operation to remove all parathyroid glands and reimplant 30 to 40 mg in the forearm if REFRACTORY to medical management
HYPERPARATHYROIDISM (HPTH) Why place 30 to 40 mg of sliced parathyroid gland in the forearm? P457
To retain parathyroid function; if HPTH
recurs, remove some of the parathyroid
gland from the easily accessible forearm
HYPERPARATHYROIDISM (HPTH) What must be ruled out in the patient with HPTH from hyperplasia? P457
MEN type I and MEN type IIa
HYPERPARATHYROIDISM (HPTH) What carcinomas are commonly associated with hypercalcemia? P457
Breast cancer metastases, prostate
cancer, kidney cancer, lung cancer,
pancreatic cancer, multiple myeloma
HYPERPARATHYROIDISM (HPTH) What is the most likely diagnosis if a patient has a PALPABLE neck mass, hypercalcemia, and elevated PTH? P457
Parathyroid carcinoma (vast majority
of other causes of primary HPTH have
nonpalpable parathyroids)
PARATHYROID CARCINOMA
What is it?
P457
Primary carcinoma of the parathyroid
gland
PARATHYROID CARCINOMA
What is the number of
glands usually affected?
P457
1
PARATHYROID CARCINOMA
What are the signs/
symptoms?
P457
Hypercalcemia, elevated PTH, PALPABLE parathyroid gland (50%), pain in neck, recurrent laryngeal nerve paralysis (change in voice), hypercalcemic crisis (usually associated with calcium levels > 14)
PARATHYROID CARCINOMA
What is the common tumor
marker?
P457
Human Chorionic Gonadotropin
HCG
PARATHYROID CARCINOMA
What is the treatment?
P457
Surgical resection of parathyroid mass
with ipsilateral thyroid lobectomy,
ipsilateral lymph node resection
PARATHYROID CARCINOMA What percentage of all cases of primary HPTH are caused by parathyroid carcinoma? P458
1%
PARATHYROID CARCINOMA POSTOPERATIVE COMPLICATIONS OF PARATHYROIDECTOMY What are the possible postoperative complications after a parathyroidectomy? P458
Recurrent nerve injury (unilateral: voice change; bilateral: airway obstruction), neck hematoma (open at bedside if breathing is compromised), hypocalcemia, superior laryngeal nerve injury
PARATHYROID CARCINOMA POSTOPERATIVE COMPLICATIONS OF PARATHYROIDECTOMY What is “hungry bone syndrome”? P458
Severe hypocalcemia seen after surgical
correction of HPTH as chronically
calcium-deprived bone aggressively
absorbs calcium
PARATHYROID CARCINOMA POSTOPERATIVE COMPLICATIONS OF PARATHYROIDECTOMY What are the signs/ symptoms of postoperative hypocalcemia? P458
Perioral tingling, paresthesia,
+ Chvostek’s sign, + Trousseau’s sign,
+ tetany
PARATHYROID CARCINOMA POSTOPERATIVE COMPLICATIONS OF PARATHYROIDECTOMY What is the treatment of hypoparathyroidism? P458
Acute: IV calcium
Chronic: PO calcium, and vitamin D
PARATHYROID CARCINOMA
POSTOPERATIVE COMPLICATIONS OF PARATHYROIDECTOMY
What is parathyromatosis?
P458
Multiple small hyperfunctioning parathyroid tissue masses found over the neck and mediastinum—thought to be from congenital rests or spillage during surgery—remove surgically (RARE)
