Parathyroid/ pituitary Flashcards
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
What defines tertiary hyperparathyroidism?
Tertiary hyperparathyroidism = autonomous secretion of PTH even after correction of secondary hyperparathyroidism (e.g. kidney transplant) OR secondary hyperparathyroidism that have hypercalcemia that is refractory to medical management
- High Ca and high PTH, low phos
- Initial management is medical likely 2ndary
- Surgical indications: Refractory to treatment hypercalcemia or basically any symptoms
- Surgery:
- All need 4 quadrant BL exploration
- Subtotal parathyroidectomy (resect 3 glands) (best)
What is familial hypocalciuric hypercalcemia?
Familial hypocalciuric hypercalcemia – Autosomal dominant
- slightly high PTH and Ca. Low phosphate, high chloride, Low urine Ca (24 urine Ca < 100 = diagnostic)
- Defect in Ca receptor in kidney not detecting Ca, causing increased PTH, which causes increased Ca resorption in kidney
- Defect in CASR gene
Bilateral 4 quadrant neck exploration is needed for:
- No 50% drop in PTH intra op only resect enlarged glands
- Negative pre-operative localization surgery
- For all 2ndary and tertiary hyperparathyroidism
- 4 glands enlarged disease If MEN I or IIa
- If 2-3 enlarged parathyroid – excise all of them
If can’t find intra-op:
- 1st explore all 4 glands- must do this in MEN syndrome for all
- Never resect normal glands, never biopsy normal glands
- If missing inferior gland check #1 thymus, and then intra-thyroidal
- If missing superior gland #1Tracheoesophageal groove, #2 retroesophageal, carotid sheathe, and paraesophageal spaces
- Never do median sternotomy at initial operation
Re-exploration parathyroidectomy
- Higher chance of recurrent laryngeal injury and hypothyroidism
Post op hypocalcemia
- Check calcium levels only if symptomatic. Start with oral calcium and vitamin D
- IV calcium only for severe symptoms: tetany, seizures, prolonged QT, calcium < 7.5
- Perioral and hand numbness is not severe
- Bone hunger: Normal PTH and low HCO3, low phosphate and mg
- Graft/remnant failure – low PTH and normal HCO3
Parathyroid CA
- Ca > 14, and PTH > 300
- en bloc resection, with adjacent thyroid lobe AND central neck dissection, MRND if nodes affected
- Cinacalcet: treatment of hypercalcemia associated with parathyroid CA
- MC mets to lung
MEN I
-Parathyroid hyperplasia 90% chance - 1st to be symptomatic. Need to fix this first
-Pancreatic 40% - Gastrinoma #1 – MCC of mortality
-Pituitary 40% - #1 prolactinoma
MEN IIa
- Parathyroid hyperplasia 25%
- Medullary thyroid cancer 90% - first to be symptomatic: Diarrhea. MCC of mortality
- Pheochromocytoma 50%- nearly always benign. Treat this first
MEN IIb
-Medullary thyroid cancer 90% - first to be symptomatic: Diarrhea. MCC of mortality
-Pheochromocytoma 50%- nearly always benign. Treat this first
-Mucosal neuromas, Marfan’s habits, musculoskeletal abnormalities
Posterior pituitary
ADH – supraoptic nuclei. Osmolar receptors in the hypothalamus (high osmolarity increases release or low volume)
Oxytocin – paraventricular nuclei
Anterior pituitary
No direct blood supply; from portal venous blood by passing neurohypophysis first
Releases: ACTH, TSH, GH, LH, FSH, prolactin
Bi-temporal hemianopia
Pituitary mass compressing optic nerve (CN II) at chasm
CI to transsphenoidal resection
Supracellar extension (dumbbell shaped), massive lateral extension
Bromocriptine
dopamine agonist; can be used for all endocrine tumors in pituitary except ACTH
Prolactinoma
MC pituitary tumor. MC microadenoma
Most don’t need surgery
Tx:
-Asymptomatic and Microadenoma < 1 cm: follow MRI
-Symptomatic or macro > 1 cm: Bromocriptine or cabergoline.
-Transphenoidal resection for failed medical tx, hemorrhage, visual loss, wants pregnancy, or CSF leak
Acromegaly
-Insulin like growth factor – best test. MRI.
MC macroadenoma.
Surgery is 1st line: Transphenoidal resection.
Pegvisomant: GH receptor antagonist
Sheehan’s syndrome
-Anterior pituitary ischemia 2/2 hemorrhage & hypotensive episode during child birth
-Trouble lactating, amenorrhea, hypothyroidism, adrenal insufficiency
-Tx: corticosteroids, hormone replacement
Pituitary apoplexy
Bleeding into a pituitary tumor with subsequent destruction of the gland
-Tx: corticosteroids, hormone replacement
Craniopharyngioma – Benign. MC children. Treatment is surgery if symptomatic.
Craniopharyngioma – Benign. MC children. Treatment is surgery if symptomatic. Diabetes insidious is frequent complication postoperatively.
BL pituitary masses
MC mets
Young patient, primary hyperparathyroidism wiht multigland disease…next best step
Genetic testing. Primary hyperparathyroidism is often earlist manifestation of MEN1. Changes opperative approach. MEN1= subtotal parathyroidectomy. MEN2A resect visibly enlarged glands.
