Parathyroid/ pituitary Flashcards
(46 cards)
Where is the superior parathyroid gland located?
Found posterior to the recurrent laryngeal nerve (RLN) and superior to the inferior thyroid artery.
If not here then: tracheoesophageal groove
Where is the inferior parathyroid gland located?
Anterior to the RLN and below the inferior thyroid artery.
If not here then: thyrothymic ligament
What is the function of parathyroid hormone (PTH)?
Absorbs calcium in the kidney, decreases bicarbonate (HCO3) and phosphate (PO4) absorption in the kidney, and increases calcium and phosphate by bone absorption through osteoclast activation. Activates Vit D.
What is the net effect of PTH on calcium and phosphate levels?
Net decrease in phosphate and increase in calcium.
What is the role of calcitonin?
Made by parafollicular C cells
Causes kidney calcium and phosphate excretion, inhibits calcium and phosphate resorption from bone by osteoclast inhibition.
What is the pathway for vitamin D synthesis?
7-dehydrocholesterol –> ingested or UV light –> Vitamin D3 –> liver (25-OH) –> Vitamin D3-25OH –> kidney (1-hydroxylation) –> 1,25-dihydroxycholecalciferol.
What does vitamin D do?
Increases intestinal calcium and phosphate absorption by activation of calcium binding protein.
What is the normal range for PTH?
10-16 pg/mL.
What cells produce PTH?
Made by chief cells in the parathyroid glands.
What triggers the release of PTH?
Released in response to low calcium and low vitamin D levels.
So patients with low vitamin D will have high PTH, must correct vitamin D before diagnosis of PHPT
What is the most common cause of primary hyperparathyroidism?
A single adenoma (80% of cases).
10-15% caused by hyperplasia, 4% more than 1 adenoma
What is the most common cause of hypercalcemia in the outpatient setting?
Primary hyperparathyroidism (PHPT).
Inpatient its cancer
What laboratory findings are associated with hyperparathyroidism?
High calcium, high PTH, low phosphate (may not be low if renal failure), Cl:phosphate ratio > 33, high urinary calcium
Labs can be subtle: A high Ca and a high normal PTH is still consistent with PHPT
Cl:phosphate ratio > 33
- PTH increases chloride levels
- Hyperchloremic metabolic acidosis
Increase in urine cAMP – unlike FHH
What is osteitis fibrosa cystica?
Bone lesions from calcium resorption, characteristic for primary hyperparathyroidism.
What is the first step in preoperative localization for parathyroid surgery?
Get an ultrasound of the neck and localize with a sestamibi scan with SPECT.
-If above did not localize: Next step is CT
-Sestamibi scan – used to find ADENOMAS. Not good for hyperplasia
What are surgical indications for parathyroidectomy?
All patients with symptoms: pancreatitis, kidney stones, cholelithiasis, PUD, constipation, depression, bone pain, osteoporosis
Asymptomatic patients with significant lab findings: serum/urinary calcium, creatine clearance, T-score <-2.5 or vertebral fracture
What is the treatment for a single adenoma in hyperparathyroidism?
Resect the adenoma.
What is the treatment for 4-gland hyperplasia?
Remove all 4 glands and re-implant half of a gland into the brachioradialis muscle.
- Must re-implant into arm for MEN syndrome!!!!!
- Other option is to resect 3 ½ and leave ½ in place, avoid this in MEN syndrome, b/c if you need to re-operative = poor tissues
parathyroid intraoperative procedure
- Sit patient with head up (semi-Fowler’s position) (beach chair position), with arms tucked
- Transverse incision 2 finger breathes above sternal notch
- Make subplatysmal flap, superior flap to cricoid cartilage, inferior flap to sternal notch.
- Divide midline raphe of strap mm
- Dissect between muscles and thyroid (stay close to thyroid to avoid injury to RLN)
- If adenoma, find the one targeted. Get pre-op PTH, then resect and send for frozen, check PTH immediately after excision, then in 5, 10, AND 20 minutes. Should drop by 50%.
What is the Miami criteria for intraoperative PTH monitoring?
A 50% drop in PTH compared to preoperative or highest intraoperative value before excision.
-If doesn’t drop need to explore all the other glands
What is the most common cause of post-operative persistent hyperparathyroidism?
Missed adenoma in the neck. Get sestamibi scan
What is the most common cause of secondary hyperparathyroidism?
Secondary hyperparathyroidism = hyperplasia
MCC is kidney disease, also caused by Vitamin D deficiency (low 1,25 OH hydroxyvitamin D)
Very High PTH, low-normal Ca, high PO4 (kidney disease)
What is calciphylaxis?
Calciphylaxis – renal failure and 2ndary hyperparathyroidism.
- Ca-phos deposit in medium sized vessels.
- Sx: skin necrosis. DX: skin biopsy (calcium deposits).
- Tx: Do not debride. Treatment is parathyroidectomy. Can try sodium thiosulfate, cinacalcet
Medical Tx:
- sevelamer chloride (binds phosphate), calcitriol, Ca supplement
- Cinacalcet – increases sensitivity of parathyroid to Ca decreases PTH, Ca, and phos
Surgical indications:
- Maxed out on cinacalcet/not tolerating, still with high PTH or phos
- PTH > 800
- Intractable symptoms, pruritis, bone pain
- Calciphylaxis
Surgical treatment:
- All need 4 quadrant BL exploration
- Subtotal parathyroidectomy (resect 3 glands) (preferred) but can also do total parathyroidectomy and implant in forearm
Persistently high PTH and phosphorous associated with CV morbidity, fractures, and mortality!!
What is the treatment for pseudohypoparathyroidism?
Pseudohypoparathyroidism – Kidney insensitivity to PTH
Low Ca, high Phosphate, high PTH
Patients usually short, obese, stubby fingers with dimpling of knuckles with fist
Tx: oral calcium and vit D
