Parathyroid Pathology Singh

Question 1

Describe histology of parathyroid gland

Answer 1

• Chief cells
• Oxyphil cells
• Adipocytes

Question 2

Function of the parathyroid gland?

Answer 2

• calcium homeostasis
  
  • PTH causes direct release of calcium from bone and exerts effects on kidneys
    
    • Ca reabsorption and phosphate reabsoption blocking
    • Convert inactive Vit D to active

Question 3

Low serum calcium results in ___ PTH secretion.

Answer 3

Low serum calcium results in increased PTH secretion.

Question 4

Primary Hyperparathyroidism lab values & causes?

Answer 4

• Parathyroids are secreting too much PTH so it is high as well as calclium
• Adenoma (85-95%), Primar y hyperplasia (5-10%), Parathyroid carcinoma (~1%)

Question 5

What are the sx of primary hyperparathyroidism?

Answer 5

• Painful bones, renal stones, abdominal groans and psychic moans
• Osteoporosis, nephrolithiasis, constipation/gallstones, depression/lethargy/seizures

Question 6

What is Osteitis Fibrosis Cystica (von Recklinghausen’s disease of bone)

Answer 6

• Starts as a brown tumor with osteoclast driven bone destruction that results in small fractures and hemorrhage and reactive tissues

Question 7

What can osteitis fibrosis cystica be mistaken for?

Answer 7

Metastatic disease

Question 8

How does hyperparathyroidism in the book comapre to real life?

Answer 8

Most primary hyperparathyroid cases are asymptomatic and discovered incidentally though routine lab work with an elevated Ca level

Question 9

What type of scan is done to diagnose parathyroid adenoma?

Answer 9

Technetium scan, this shows an increased uptake disproportionate to other glands

Question 10

Describe parathyroid adenoma

Answer 10

• benign neoplasm of parathyroid chief or oxyphil cells
• usually solitary and surrounded by rim of normal parathyorid tissue
  
  • can cause other glands to shrink due to the excessive PTH from the adenoma

Question 11

Describe primary hyperplasia of parathyroids causing primary hyperparathyroidism.

Answer 11

• Almost always in multiple glands
• MEN sysndromes may be responsible
• NO normal rim of parathyroid tissue → lacking normal tissue next to it as seen in an adenoma (no adipocytes)

Question 12

Describe parathyotid carcinoma.

Answer 12

• Metastasis is the tell tale sign
• one of the causes of primary hyperparathyroidism
• Has features of invasion to adjacent tissues and vascular invasion
• Elevated PTH doesn’t go down after surgery

Question 13

High calcium level but suppresed PTH, what causes this?

Answer 13

• Hypercalcemia of Malignancy
• vitamin D excess
• excess calcium ingestion
• medications (thiazide’s)

Question 14

What is the difference between hypercalcemia casued by hyperparathyroidism and non paathyroid sources?

Answer 14

Hyperparathyroidism:

• likely asx
• commonly due to PT adenoma

Non PT sources:

• more likely to be symptomatic → mental status changes, n/v, QT interval shortened

Question 15

What are the mechanisms of malignant hypercalcemia?

Answer 15

• Humoral hypercalcemia of malignancy is related to PTHrP (80%) which is analogous to PTH and related to squamous carcinomas
  
  • there is also Vitamin D mediated pathway which is seen in lymphomas
• Local osteolytic hypercalcemia
  
  • release of ca due to osteoclastic bone resorption
    
    • breast carcinoma and myeloma

Question 16

Clinical features of hypocalcemia?

Answer 16

• Behavioral disturbances/stupor
• numbness and parasthesias
• muscle cramps and tetany
  
  • trosseau sign +
  • Chvostek sign +
• convulsions

Question 17

Renal Osteodystrophy?

Answer 17

• Dissecting osteitis in hyperparathyroidism
• In secondary hyperparathyroidism renal osteodystrophy can lead to rugger jersey sign

Question 18

What is Calciphylaxis (calcific uremic ateriolopathy)?

Answer 18

• Secondary hyperparathyroidism in assoc. with renal disease that is assoc. with extensive calcification and occlusion of blood vessels resulting in ischemia
• Patients die from sepsis

Question 19

Describe tertiary HPT?

Answer 19

• calcium and PTH high (same as primary HPT)
• Tertiary HPT comes out of patient who historically had secondary hyperparathyroidism first
  
  • it went on for so long and eventually got cured but now body releases excess PTH

Question 20

What causes primary hypoparathyroidism and what are the lab values?

Answer 20

• Low calcium and low PTH
• Acquired:
  
  • Iatrogenic is the most common cause
  • also caused by autoimmune attack
• can be congenital:
  
  • DiGeorge
  • CASR
  • Familial Isolated Hypoparathyroidism

Question 21

Describe DiGeorge syndrome in relation to the parathyroid glands.

Answer 21

• sometimes the parathyroid glands are affected
• can have tetany due to hypocalcemia from parathyroid hypoplasia/aplasia

Question 22

What are the two types of CaSR mutations?

Answer 22

Inactivating CaSR (loss of function):

• body believes there isn’t enough calcium even when there is
• turns on PTH → hypercalcemia
• reduces renal excretion → hypocalciuria
• Called Familial Hypocalcuric hypercalcemia

Activating CaSR (gain function):

• body thinks there is plenty of calcium when there isn’t
• turns off PTH → hypocalcemia
• increases renal excretion → hypercalciuria
• Called AD hypoPTH Hypercalciuric hypocalcemia

Question 23

What are labs seen in psuedohypoparathyroidism?

Answer 23

• normal or elevated PTH
• Hypocalcemia and hyperphosphatemia
• resistance to PTH

Question 24

What is Albright’s Hereditary Osteodystrophy?

Answer 24

• short stature and obesity
• shortened fingers and toes
• occasionally seizures and tetany
• assoc. with psuedohypoparathyroidism