Parathyroid

Question 1

Superior parathyroids

Answer 1

4th pouch; lateral to RLNs; above inferior thyroid artery

Question 2

Inferior parathryoids

Answer 2

3rd pouch; associated with thymus; medial to RLNs, below inferior thyroid artery; more variable location

Question 3

Ectopic parathyroids

Answer 3

tail of thymus (most common); intrathyroid, mediastinal, tracheoesophageal groove

Question 4

Inferior thyroid artery

Answer 4

blood supply to both superior and inferior parathyroid glands

Question 5

PTH

Answer 5

increases serum Ca
increases Ca reabsorption in distal convoluted tubule
increases osteoclasts to release Ca
increases vit D production in kidney (1-OH hydroxylation) which increases Ca binding protein in intestine which increases intestinal Ca reabsorption

Question 6

Vit D

Answer 6

increases intestinal Ca and PO4 absorption by increasing Ca-binding protein

Question 7

Calcitonin

Answer 7

decreases serum Ca; decreases bone Ca resorption (osteoclast inhibition); increase urinary Ca & PO4 excretion

Question 8

Most Common Cause of Hypoparathyroidism

Answer 8

previous thyroid surgery

Question 9

Primary Hyperparathyroidism

Answer 9

PRAD-1 oncogene increases risk of adenomas; women; older age; due to autonomously high PTH; dx with increase Ca, decrease phosphorous; Cl- to phos ration > 33; hyperchloremic metabolic acidosis; most pts have no symptoms (increase Ca on routine labs)

Question 10

Osteitis fibrosa cystica

Answer 10

brown tumors; bone lesions from Ca resorption; characteristic of hyperparathyroidism

Question 11

Hyperparathyroidism symptomss

Answer 11

muscle weakness, myalgia, AMS, nephrolithiasis, pancreatitis, PUD, depression, bone pain, pathologic fractures, constipation, N/V, anorexia

Question 12

Hyperparathyroidism Indications for Surgery

Answer 12

serum Calcium > 1mg/dL above upper limits of normal

bone density > 2 SD below peak bone mass (T-score

Question 13

Primary Hyperparathyroidsm

Answer 13

single adenoma 80%
multiple adenomas 4%
diffuse hyperplasia 15%; pts with MEN I or IIa have 4 gland hyperplasia
parathyroid adenocarcinoma very rare; can get very high Ca levels

Question 14

Parathyroid adenoma tx

Answer 14

resection; inspect other glands to r/o hyperplasia or multiple adenomas; intraop PTH level should go down 50%

Question 15

Parathyroid hyperlasia

Answer 15

do not biopsy all glands; resect 3.5 glands or total parathyroidectomy & autoimplantation

Question 16

Parathyroid CA

Answer 16

need radical parathyroidectomy (need to take ipsilateral thyroid)

Question 17

Parathyroidism in pregnancy

Answer 17

surgery in 2nd trimester; increase risk of stillbirth if not resected

Question 18

PTH half life

Answer 18

10 minutes

Question 19

Missing gland

Answer 19

check inferiorly in thymus tissue (most common ectopic location), near carotids, thyroid; still cannot find gland, close and follow PTH; if still high get parathyroid scan to localize; some say perform thyroidectomy on side in which only one gland was found; at reoperation for missing gland most common location is normal anatomic position

Question 20

Secondary hyperparathyroidism

Answer 20

seen in pts with renal failure; increase PTH in response to low Ca; most do not need surgery; tx PO4 binders; surgery for bone pain, fractures or pruritus

Question 21

Tertiary hyperparathyroidism

Answer 21

kidney transplant but still overproduces PTH; tx total parathyroid with autoimplantation

Question 22

Familial Hypercalcemic Hypocalciuria

Answer 22

increase serum Ca and decrease urine Ca (should be increased if hyperparathyroid); caused by defect in PTH receptor in distal convoluted tubule of kidney that causes increase resorption of Ca; dx Ca9-11, normal PTH, decrease urine Ca; tx nothing

Question 23

Pseudohypoparathyroidism

Answer 23

defect in PTH receptor in kidney; does not respond to PTH

Question 24

Parathyroid Ca

Answer 24

rare cause of hypercalcemia; 50% 5 year survival rate; mortality is due to hypercalcemia; increase Ca, PTH & ALP; lung most common location for mets; tx wide en bloc excision (parathyroidectomy & ipsilateral thyroidectomy; recurrence 50%

Question 25

MEN Syndromes

Answer 25

derived from APUD cells; neoplasms can develop synchronously or metachronously; Autosomal dominant, 100% penetrance, variable expressivity

Question 26

MEN I

Answer 26

MENIN gene Parathyroid hyperplasia Pancreatic islet cell tumors (gastrinoma #1, 50% multiple & malignant, major morbidity of syndrome) Pituitary adenoma (prolactinoma #1)

Question 27

MEN 2a

Answer 27

RET protooncogene Parathyroid hyperplasia Pheochromocytoma (often bilateral, almost always benign, correct 1st) Medullary Ca of Thyroid (diarrhea most common sx; often bilateral; #1 cuase of death in these pts; usually 1st to be symptomatic)

Question 28

MEN IIb

Answer 28

Pheochromocytoma (correct 1st) Medullary Ca of Thryoid Marfan's, mucosal neuromas

Question 29

Hypercalcemia

Answer 29

``` Malignancy (hematologic 25% - lytic bone lesions; nonhematologic 75% - cancers that release PTHrp: small cell lung CA, breast CA) Hyperparathyroid ; hyperthyroid Familial hypercalcemic hypocalciuria Immobilization Granulomatous disease (Sarcoid / TB) Excess Vit D Milk-alkali syndrome (excessive intake milk & calcium) Thiazide diuretics ```

Question 30

Hypercalcemic crisis

Answer 30

fluids, furosemide, dialysis