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CHAPTER 23- PARATHYROID.txt

  1. Superior parathyroids
    • 1) 4th pouch
    • 2) associated with thyroid complex
    • 3) lateral to recurrent laryngeal nerves (RLNs)
    • 4) posterior surface of superior portion of the gland
    • 4) above inferior thyroid artery
  2. Inferior parathyroids
    • 1) 3rd pouch
    • 2) associated with thymus
    • 3) Medial to RLNs
    • 4) more anterior
    • 5) below inferior thyroid artery
    • 6) inferior parathyroids have more variable location and are more likely to be ectopic
    • 7) occasionally are found in the tail of the thymus (most common ectopic site) and can migrate to the anterior mediastinum
  3. Other ectopic sites of parathyroids:
    • 1) intrathyroid
    • 2) near tracheoesophageal groove
    • 3) mediastinal
  4. What percentage of people have all 4 parathyroid glands?
    90%
  5. What is the blood supply to the superior and inferior parathyroid glands
    inferior thyroid artery
  6. PTH:
    • 1) increases serum calcium
    • 2) increases kidney calcium reabsorption in the distal convoluted tubule, decreases PO4 absorption
    • 3) increases osteosclasts in bone to release Ca (and PO4-)
    • 4) increased vitamin D production in kidney (increase 1-OH hydroxylation)--> increased Ca-binding protein in intestine--> increased intestinal Ca reabsorption
  7. Vitamin D
    increases intestinal Ca and PO4 absorption by increasing calcium-binding protein
  8. Calcitonin
    • 1) decreases serum calcium
    • 2) decreases bone calcium resorption (inhibits osteoclasts)
    • 3) increases urinary Ca and PO4- excretion
  9. Normal Ca level (total and ionized):
    Normal PTH level:
    Normal PO4 level:
    Normal Cl- level:
    • Normal Ca level (total and ionized): 8.5-10.5/4.4-5.5
    • Normal PTH level: 5-40
    • Normal PO4 level: 2.5-5
    • Normal Cl- level: 98-107
  10. Whats the most common cause of hypoparathyroidism
    previous thyroid surgery
  11. Primary hyperparathyroidism:
    • 1) PRAD-1 oncogene increases the risk of adenomas
    • 2) Women, older age
    • 3) due to automomously high PTH
    • 4) Dx:
    • 1- increased Ca
    • 2- decreased Phosphorous
    • 3- Cl to phosphorous ratio >33
    • 4- increased renal cAMP
    • 5- HCO3- secreted in urine
    • 5) can get hyperchloremic metabolic acidosis
  12. Osteitis fibrosa cystica (brown tumors)
    bone lesions from Ca resorption, characteristic of hyperparathyroidism
  13. How does hyperparathyroidism present?
    most patients have no symptoms- increased Ca found on routine lab work for some other problem or on checkup
  14. Symptoms of Hyperparathyroidism:
    • 1) muscle weakness
    • 2) myalgia
    • 3) nephrolithiasis
    • 4) pancreatitis
    • 5) Peptic ulcer disease
    • 6) depression
    • 7) bone pain
    • 8) pathologic fractures
    • 9) mental status changes
    • 10) constipation
    • 11) nausea and vomiting
    • 12) anorexia
    • 13) hypertension can result from renal impairment
  15. Diagnositic workup for primary hyperparathyroidism
    • 1) take careful history, including records of medications, symptoms, prior head and neck radiotherapy, and other endocrinopathies in the patient and the patient's family.
    • 2) establish elevated calcium through 2 or 3 determinations
    • 3) order a chest radiograph and search for bony metastases, sarcoidosis, and pulmonary tumors
    • 4) order an excretory urogram and search for nephrolithiasis and rarely, renal tumors
    • 5) order a serum protein electrophoresis to rule out multiple myeloma
    • 6) order a 24-hour urinary calcium determination (benign familial hypocalciuric hypercalcemia)
    • 7) rule out multiple endocrine neoplasia (usually MEN type I)
    • 8) check the absolute or relative elevation of the PTH level.
  16. Surgical indications for primary hyperparathyroidism:
    1) symptomatic disease

    • 2) asymptomatic disease with:
    • 1- Ca >13
    • 2- decreased Cr clearance
    • 3- kidney stones
    • 4- substantialaly decreased bone mass
  17. What percentage of people with primary hyperparathyroidism have a single adenoma? Multiple adenomas? Diffuse hyperplasia
    • Single adenoma- 80%
    • Multiple adenomas- 4%
    • Diffuse hyperplasia- 15%; patients with MENI or IIa have 4 gland hyperplasia
  18. Parathyroid adenocarcinoma:
    very rare; can get very high Ca levels
  19. Treatment for primary hyperparathyroidism:
    • Adenoma-
    • 1) resection; inspect other glands to rule out hyperplasia or multiple adenomas

    • Parathyroid hyperplasia-
    • 1) do not biopsy all glands--> risks hemorrhage and hypoparathyroism.
    • 2) Resect 3.5 glands or total parathyroidectomy and autoimplantation

    • Parathyroid Ca
    • 1) need radical parathyroidectomy (need to take ipsilateral thyroid)
  20. hyperparathyroidism and preganancy?
    surgery in 2nd trimester; increased risk of stillbirth if not resected
  21. How do you confirm that the tissue taken was indeed parathyroid?
    intraop frozen section
  22. Intraop PTH levels
    • 1) can help determine if the causative gland is removed (PTH should go to <1/2 the preop value)
    • 2) PTH half-life is <10minutes
  23. Where should you look if you are missing a gland?
    • 1) check inferiorly in thymus tissue (most commonly ectopic location)
    • 2) near carotids
    • 3) vertebral body
    • 4) superior to pharynx
    • 5) thyroid
  24. If you still cannot find gland:
    • 1) close and follow PTH
    • 2) if PTH still elevated, get parathyroid scan to localize
    • 3) some say perform thyroidectomy on the side in which only one gland was found
  25. At reoperation for missing gland:
    1) most common location for the gland is normal anatomic position
  26. Postop hypocalcemia-
    • 1) caused by bone hunger
    • 2) hypomagnesemia
    • 3) failure of the parathyroid remnant or graft
  27. Persistent hyperparathyroidism -
    (1%) most commonly due to a missed adenoma remaining in the neck
  28. Recurrent hyperparathyroidism:
    • 1) occurs after a period of hypocalcemia or nornocalcemia
    • 2) can be due to a new adenoma formation
    • 3) can be due to tumor implants at the original operation that have now grown
    • 4) need to consider recurrent parathyroid Ca
  29. What is reoperation associated with?
    • 1- increased risk of RLN injury
    • 2- permanent hypoparathyroidism
  30. Hypocalcemia postop:
    • 1) Bone hunger- normal PTH, decreased HCO3-
    • 2) Aparathyroidism- decreased PTH, normal HCO3-
  31. Sestamibi-technectium-99
    • 1) will have preferential uptake by the overactive parathyroid gland
    • 2) good for picking up adenomas but not 4-gland hyperplasia
    • 3) best for trying to pick up ectopic glands
  32. Secondary hyperparathyroidism
    • 1) seen in patients with renal failure
    • 2) increased PTH in response to low Ca
    • 3) most do not need surgery (90%)
    • 4) ectopic calcification and osteoporosis can occur
    • 5) Tx:
    • 1- control diet PO4
    • 2- PO4-binding gel
    • 3- decrease aluminum
    • 4- calcium supplement
    • 5- vitamin D
    • 6- calcium in dialysate
  33. When do you perform surgery in secondary hyperparathyroidism and what does the surgery involve?
    • Surgery for:
    • 1- bone pain ( most common indication; 80-90% get relief)
    • 2- fractures
    • 3- pruritis

    2) surgery involves total parathyroidectomy with autotransplantation or subtotal parathyroidectomy
  34. Tertiary hyperparathyroidism
    • 1) renal disease now corrected with transplant, but still overproducing PTH
    • 2) has similar lab values as primary hyperparathyroisim (hyperplasia)
    • 3) Tx:
    • 1- subtotal (3.5 glands) or total parathyroidectomy with autoimplantation)
  35. Familial hypercalcemic hypocalciuria
    • 1) patients have increased serum calcium and decreased urine calcium (should be increased if hyperparathyroidism)
    • 2) caused by defect in PTH receptor in distal convoluted tubue of the kidney that causes increase resorption of calcium
    • 3) Dx:
    • 1- Calcium 9-11
    • 2- normal PTH (30-60)
    • 3- decreased urine Ca
    • 4) Tx:
    • 1- nothing (calcium generally not that high in these patients)
    • 2- no parathyroidectomy
  36. Pseudohypoparathyroidism:
    because of defect in PTH receptor in the kidney, does not respond to PTH
  37. Parathyroid cancer
    • 1) rare cause of hypercalcemia
    • 2) 50% 5 year survival rate
    • 3) mortality is due to hypercalcemia
    • 4) increased Ca, PTH, and alkaline phosphatase (can have extremely high Ca levels)
    • 5) lung is most common location for metastases
    • 6) Tx: wide en block excision (parathyroidectomy and ipsilateral thyroidectomy)
    • 7) recurrence in 50%
  38. Multiple endocrine neoplasia syndromes
    • 1) derviced from APUD cells (amine precursor uptake decarboxylase)
    • 2) neoplasma can develop synchronously or metachronously
    • 3) autosomal dominant, 100% penetrance, variable expressivity
  39. MEN I
    • Pituitary Adenoma
    • 1- prolactinoma #1
    • 2- need to correct hyperparathyroidism 1st

    • Parathyroid hyperplasia
    • 1- usually the first part to become symptomatic; urinary symptoms
    • 2- Tx: 4 gland resection with autotransplantation

    • Pancreatic islet cell tumors
    • 1- gastrinoma #1
    • 2- 50% multiple, 50% malignant-major morbidity of syndrome
  40. MEN IIa
    Parathyroid hyperplasia

    • Medullary Ca of thyroid
    • 1- nearly all patients; diarrhea most common symptom; often bilateral
    • 2- #1 cause of death in these patients
    • 3- usually 1st part to be symptomatic
    • 4- need to correct pheochromocytoma 1st

    • Pheochromocytoma
    • 1- very often bilateral, nearly always benign
  41. MEN IIb
    • Pheochromocytoma
    • 1- very often bilateral, nearly always benign

    • Medullary Ca of thyroid
    • 1- nearly all patients; diarrhea most common symptoms; often bilateral
    • 2- #1 cause of death in these patients
    • 3- usually 1st part to be symptomatic

    • - Mucosal neuromas
    • - Marfan's habitus, musculoskeletal abnormalities

    Need to correct pheochromocytoma first
  42. Name the gene for MEN I:
    MENIN gene
  43. Name the gene for MEN II
    RET proto-oncogene
  44. See table on pg 145:
    Disease Phenotypes Related to Mutation of the RET proto-oncogene
  45. Causes of Hypercalcemia
    • 1) Malignancy
    • 1- hematologic (25%)- lytic bone lesions
    • 2- Nonhematologic (75%)- cancers release PTHrp (small cel lung Ca, breast Ca)
    • 2) hyperparathyroidism
    • 3) hyperthyroidism
    • 4) familial hypercalcemic hypocalciuria
    • 5) immobilization
    • 6) granulomatous disease (sarcoidosis or tuberculosis)
    • 7) excess vitamin D
    • 8) milk-alkali syndome (excessive intake of milk and calcium supplements)
    • 9) thiazide diuretics
  46. Mithramycin
    • 1) inhibits osteoclasts (used with malignancies or failure of conventional treatment)
    • 2) has hematologic, liver, and renal side effects
  47. Hyercalcemic crisis
    • 1) usually secondary to another surgery
    • 2) Tx:
    • 1- fluids
    • 2- furosemide
    • 3- dialysis
  48. Breast Ca metastases to bone
    • 1) release PTHrp; can cause hypercalcemia
    • 2) small cell lung Ca and other nonhematologic cancers can do this as well--> this is not due to bone destruction
    • 3) associated with increased urinary cAMP (from action of PTHrp on kidney
  49. Hematologic malignancies
    1) these can cause bone destruction; can slo increase Ca and urinary cAMP will be low
Author
scottmreis
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CHAPTER 23- PARATHYROID.txt
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