Chapter 23: Parathyroid Flashcards
1
Q
Where are the superior parathyroids found?
A
Lateral to the recurrent laryngeal nerves (RLNs), posterior surface of superior portion of gland, above inferior thyroid artery
2
Q
Superior parathyroids develop from what
A
4th pharyngeal pouch; associated with thyroid complex
3
Q
Inferior parathyroids develop from what
A
3rd pharyngeal pouch; associated with thymus
4
Q
Where are the inferior parathyroids found?
A
- Medial to RLNs, more anterior, below inferior thyroid artery
5
Q
Parathyroids: which ones are more likely to have a variable location and more likely to be ectopic?
A
Inferior parathyroids
6
Q
Where are the inferior parathyroids occasionally found?
A
In the tail of the thymus (most common ectopic site-thyrothymic ligament) and can migrate to the anterior mediastinum
7
Q
Ectopic sites of inferior parathyroids
A
Tail of thymus, anterior mediastinum, intra-thyroid, near tracheoesophageal groove
8
Q
% population that have all parathyroid glands
A
90%
9
Q
Artery: blood supply to both superior and inferior parathyroid glands
A
Inferior thyroid artery
10
Q
Increases serum calcium
A
PTH
11
Q
Four physiologic effects of PTH
A
- Increases kidney Ca reabsorption in the DCT, decreases kidney PO4 absorption
- Increased osteoclasts in bone to release Ca (and PO4-)
- Increased VitD production in kidney (increased 1-OH hydroxylation) -> increased Ca-binding protein in intestine -> increased intestinal Ca absorption
12
Q
Increases intestinal Ca and PO4 absorption by increasing calcium-binding protein
A
Vitamin D
13
Q
- Decreases serum Ca
- Decreases Ca resorption (osteoclast inhibition)
- increases urinary Ca and PO4 excretion
A
Calcitonin
14
Q
Normal Ca level
A
8.5 - 10.5 (ionized 4.4 - 5.5)
15
Q
Normal PTH level
A
5 - 40 pg/mL
16
Q
Normal PO4 level
A
2.5 - 5.0
17
Q
Normal Cl- level
A
98 - 107
18
Q
Most common cause of hypoparathyroidism
A
Previous thyroid surgery
19
Q
- Women, older age
- Due to autonomously high PTH
A
Primary hyperparathyroidism
20
Q
Dx: primary hyperparathyroidism
A
Increased Ca, decreased PO4-, Cl- to PO4- ratio > 33; increased renal cAMP; HCO3- secreted in urine
21
Q
ABG in primary hyperparathyroidism
A
Hyperchloremic metabolic acidosis
22
Q
Bone lesions from Ca resorption; characteristic of hyperparathyroidism
A
Osteitis fibrosa cystica (brown tumors)
23
Q
Symptoms of primary hyperparathyroidism
A
Most patients have no symptoms -> increased calcium found on routine lab work for some other problem or on checkup
24
Q
Muscle weakness, myalgia, nephrolithiasis, pancreatitis, PUD, depression, bone pain, pathologic fractures, mental status changes, constipation, anorexia
A
Primary hyperparathyroidism
- HTN can result from renal impairment
25
Diagnostic workup for primary hyperparathyroidism
- H&P. Elevated Ca thru 2-3 detrminations.
- CXR: look for bony mets, sarcoid, pulmonary tumors
- Excretory urogram: nephrolithiasis, renal tumors
- Serum protein electrophoresis to r/o multiple myeloma
- 24-hr urinary ca determination
- r/o MEN
- Check PTH level
26
Indications for surgery: primary hyperparathyroidism
- Symptomatic disease
| - Asymptomatic disease with Ca > 13, decreased Cr clearance, kidney stones, substantially decreased bone mass
27
Primary hyperparathyroidism: % pts with single adenoma
80% of patients
28
Primary hyperparathyroidism: % pts with multiple adenomas
Occur in 4% of patients
29
Primary hyperparathyroidism: % patients with diffuse hyperplasia
Occurs in 15% of patients with MEN 1 or 2a have 4-gland hyperplasia
30
Hyperparathyroidism: very rare, can get high Ca levels
Parathyroid adenocarcinoma
31
Treatment: parathyroid adenoma
Resection; inspect other glands to rule out hyperplasia or multiple adenomas
32
Treatment: parathyroid hyperplasia
- Do not biopsy all glands -> risks hemorrhage and hypoparathyroidism
- Tx: resect 3 1/2 glands or total parathryoidectomy and autoimplantation
33
Treatment: parathyroid Ca
Need radical parathyroidectomy (need to take ipsilateral thyroid lobe)
34
Treatment: primary hyperparathyroidism in pregnancy
Surgery in 2nd trimester; increased risk of stillbirth if not resected
35
What are benefits of intra op frozen section in primary hyperparathyroidism?
Can confirm that the tissue taken was indeed parathyroid
36
What are benefits of intra op PTH levels?
Can help determine if the causative gland is removed (PTH should go to
37
Where do you check for missing glands in hyperparathyroidism?
Check inferiorly in thymus tissue (MC ectopic location, can remove tail of the thymus and see if PTH drops), near carotids, vertebral body, superior to pharynx, thyroid
38
What if you still cannot find the parathyroid glands when you checked all ectopic locations?
Close and follow PTH; if PTH still increased, get sestamibi scan to localize
39
At reoperation for a missing gland, where do you look?
The most common location for the gland is normal anatomic position
40
What causes hypocalcemia post op in primary hyperparathyroidism?
From bone hunger or failure of parathyroid remnant / graft
41
Hypocalcemia postop primary hyperparathyroidism: Normal PTH, decreased HCO3-
Bone hunger
42
Hypocalcemia postop primary hyperparathyroidism: decreased PTH, normal HCO3-
Aparathyroidism
43
Primary hyperparathyroidism: most commonly due to missed adenoma remaining in the neck
Persistent hyperparathyroidism (1%)
44
What can cause recurrent hyperparathyroidism after surgery for primary hyperparathyroidism?
- Occurs after a period of hypocalcemia or normocalcemia
- Can be due to new adenoma formation
- Can be due to tumor implants at the original operation that have now grown.
- Need to consider recurrent parathyroid cancer
45
Risks of reoperation in primary hyperparathyroidism
Associated with increased risk of RLN injury, permanent hypoparathyroidism
46
- Will have preferential uptake by the overactive parathyroid gland
- Good for picking up adenomas but not 4-gland hyperplasia
- Best for trying to pick up ectopic glands
Sestamibi scan
47
- Seen in patients with renal failure
- Increased PTH in response to low Ca
- Most do not need surgery (95%)
- Ectopic calcification and osteoporosis can occur
Secondary hyperparathyroidism
48
Tx: secondary parathryoidism
- Ca supplement, vitamin D, control diet PO4, PO4-binding gel, decreased aluminum
- Surgery for bone pain (MC indication), fractures, or pruritus (80% get relief)
49
MC indication for surgery in secondary hyperparathyroidism
Bone pain
50
What does surgery involve in secondary hyperparathyroidism?
Surgery involves parathyroidectomy with autotransplantation or subtotal parathyroidectomy
51
- Renal disease now corrected with transplant but still overproduces PTH
- Has similar lab values as primary hyperparathyroidism (hyperplasia)
Tx: subtotal (3 1/2 glands) or total parathyroidectomy with autoimplantation
Tertiary hyperparathyroidism
52
Patients have increased serum Ca and decreased urine Ca (should be increased if hyperparathyroidism)
Familial hypercalcemic hypocalciuria
53
What causes familial hypercalcemic hypocalciuria?
Caused by defect in PTH receptor in distal convoluted tubule of the kidney that causes increased resorption of calcium
54
Dx: Ca 9-11, have normal PTH (30-60), decreased urine Ca
Tx?
Familial hypercalcemic hypocalciuria
Tx: nothing (Ca generally not that high in these patients); no parathyroidectomy
55
Because of defect in PTH receptor in the kidney, does not respond to PTH
Pseudohypoparathyroidism
56
- Rare cause of hypercalcemia
| - Increased Ca, PTH, and alkaline phosphatase (can have extremely high Ca levels)
Parathyroid Cancer
57
MC location for metastases in parathyroid cancer
Lung
58
Tx: parathyroid cancer
Wide en bloc excision (parathyroidectomy and ipsilateral thyroidectomy)
59
5-year survival rate: parathyroid cancer
50%
60
Mortality in parathyroid cancer
Due to hypercalcemia
61
Recurrence rate of parathyroid cancer
Recurrence in 50%
62
- Derived from APUD cells
- Neoplasms can develop synchronously or metachronously
- Autosomal dominant, 100% penetrance
Multiple endocrine neoplasia syndromes
63
Components of MEN-one
Pituitary adenoma
Parathyroid hyperplasia
Pancreatic islet cell tumors
64
Usually first part to become symptomatic in MEN one
Parathyroid hyperplasia
65
Tx: parathyroid hyperplasia in MEN-one
4-gland resection with autotransplantation
66
#1 pancreatic islet cell tumor in MEN-one
Gastrinoma #1 - 50% multiple, 50% malignant; major morbidity of syndrome
67
#1 pituitary adenoma in MEN-one
Prolactinoma #1
68
How do you begin to treat MEN-one?
Need to correct hyperparathyroidism 1st if simultaneous tumors
69
Components of MEN-IIa
Parathyroid hyperplasia
Medullary CA of thyroid
Pheochromocytoma
70
MC symptom of medullary CA of thyroid
Diarrhea
71
#1 cause of death in MEN-IIa patients
Medullary CA of thyroid
72
Usually first part to be symptomatic in MEN-IIa
Medullary CA of thyroid
73
MEN-2a:
- Nearly all patients; diarrhea most common symptom; often bilateral
- #1 cause of death in these patients
- Usually 1st part to be symptomatic
Medullary CA of thyroid
74
MEN-2a: often bilateral, nearly always benign
Pheochromocytoma
75
How do you begin to treat MEN-2a?
Need to correct pheochromocytoma 1st if simultaneous tumors
76
Components of MEN-2b
- Medullary CA of thyroid
- Pheochromocytoma
- Mucosal neuromas
- Marfan's habitus, musculoskeletal abnormalities
77
How do you begin to treat MEN-2b?
Need to correct pheochromocytoma 1st if simultaneous tumors
78
Gene affected: MEN one
MENIN gene
79
Gene affected: MEN2a and 2b
RET proto-oncogene
80
Disease phenotypes related to mutation of the RET proto-oncogene
MEN2a (60%), MEN2b (5%), FMTC (35%)
81
Germline mutations in cysteine codons of extracellular and transmembrane domains of RET
MEN2a
82
Germline activating mutation in tyrosine kinase domain or RET
MEN2b
83
Germline mutations in cysteine codons of extracellular or transmembrane domains of RET
FMTC
84
Causes of hypercalcemia
- Malignancy
- Hyperparathyroidism
- Hyperthyroidism
- Familial hypercalcemia hypocalciuria
- Immobilization
- Granulomatous disease (sarcoidosis or tuberculosis)
- Excess vitamin D
- Milk alkali syndrome
- Thiazide diuretics
85
Breakdown of hypercalcemia in malignancy
- Hematologic (25%): lytic bone lesions
| - Nonhematologic (75%): cancers that release PTHrP (small cell lung CA, breast CA)
86
Inhibits osteoclasts (used with malignancies or failure of conventional treatment); has hematologic, liver, and renal side effects
Mithramycin
87
Usually secondary to another surgery in patients with pre-existing hyperparathyroidism
- Tx?
Hypercalcemic crisis
Tx: fluids (normal saline) and furosemide (Lasix)
88
How does breast cancer metastases to bone cause hypercalcemia?
Release PTHrP (rP = related peptide); can cause hypercalcemia
- This is NOT due to bone destruction
- Associated with increased urinary cAMP (from action of PTHrP on kidney)
89
What do hematologic malignancy do to bone?
These can cause bone destruction with increased Calcium (urinary cAMP will be low)
