Parathyroid Pathology Singh Flashcards
Describe histology of parathyroid gland
- Chief cells
- Oxyphil cells
- Adipocytes
Function of the parathyroid gland?
- 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
- PTH causes direct release of calcium from bone and exerts effects on kidneys
Low serum calcium results in ___ PTH secretion.
Low serum calcium results in increased PTH secretion.
Primary Hyperparathyroidism lab values & causes?
- 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%)
What are the sx of primary hyperparathyroidism?
- Painful bones, renal stones, abdominal groans and psychic moans
- Osteoporosis, nephrolithiasis, constipation/gallstones, depression/lethargy/seizures
What is Osteitis Fibrosis Cystica (von Recklinghausen’s disease of bone)
- Starts as a brown tumor with osteoclast driven bone destruction that results in small fractures and hemorrhage and reactive tissues
What can osteitis fibrosis cystica be mistaken for?
Metastatic disease
How does hyperparathyroidism in the book comapre to real life?
Most primary hyperparathyroid cases are asymptomatic and discovered incidentally though routine lab work with an elevated Ca level
What type of scan is done to diagnose parathyroid adenoma?
Technetium scan, this shows an increased uptake disproportionate to other glands
Describe parathyroid adenoma
- 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
Describe primary hyperplasia of parathyroids causing primary hyperparathyroidism.
- 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)
Describe parathyotid carcinoma.
- 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
High calcium level but suppresed PTH, what causes this?
- Hypercalcemia of Malignancy
- vitamin D excess
- excess calcium ingestion
- medications (thiazide’s)
What is the difference between hypercalcemia casued by hyperparathyroidism and non paathyroid sources?
Hyperparathyroidism:
- likely asx
- commonly due to PT adenoma
Non PT sources:
- more likely to be symptomatic → mental status changes, n/v, QT interval shortened
What are the mechanisms of malignant hypercalcemia?
- 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
- release of ca due to osteoclastic bone resorption
Clinical features of hypocalcemia?
- Behavioral disturbances/stupor
- numbness and parasthesias
- muscle cramps and tetany
- trosseau sign +
- Chvostek sign +
- convulsions
Renal Osteodystrophy?
- Dissecting osteitis in hyperparathyroidism
- In secondary hyperparathyroidism renal osteodystrophy can lead to rugger jersey sign
What is Calciphylaxis (calcific uremic ateriolopathy)?
- 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
Describe tertiary HPT?
- 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
What causes primary hypoparathyroidism and what are the lab values?
- 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
Describe DiGeorge syndrome in relation to the parathyroid glands.
- sometimes the parathyroid glands are affected
- can have tetany due to hypocalcemia from parathyroid hypoplasia/aplasia
What are the two types of CaSR mutations?
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
What are labs seen in psuedohypoparathyroidism?
- normal or elevated PTH
- Hypocalcemia and hyperphosphatemia
- resistance to PTH
What is Albright’s Hereditary Osteodystrophy?
- short stature and obesity
- shortened fingers and toes
- occasionally seizures and tetany
- assoc. with psuedohypoparathyroidism
