Parathyroid Flashcards Preview

MHD > Parathyroid > Flashcards

Flashcards in Parathyroid Deck (20):
1

What is the parathyroid derived from?

pharyngeal pouches
-could be found in the carotid sheath, thymus and anterior mediatinum

2

Parathyroid histology

Chief cells predominate and contain glycogen and produce PTH

Oxyphil cells in small clusters, packed with mitochondria

-Fat increases with age up to 25 years, occupies 30% of adult gland

3

What does PTH do?

1. Activates osteoclasts by mobilizing calcium from bone
-increased tubular reabsorption
-increases conversion of vitamin D to active form
-decreases serum phosphate by increasing urinary excretion
-Augments GI calcium absorption

-Net effect increase calcium which has negative feedback on PTH

4

What is the most common cause of clinically apparent hypercalcemia? incidental hypercalcemia?

clinically apparent:
malignancy

incidental:
primary hyperparathyroidism

5

Hypercalcemia of Malignancy

Osteolytic metastases:
tumor
cytokines
local osteolysis
maturation of osteoclasts

-prognosis is poor, patients present at advanced stage

6

Primary Hyperparathyroidism
age group

50 years old
Sporadic or familial
1. Parathyroid adenoma (85-95%)
2. Primary Hyperplasia (diffuse or nodular) 5-10%
3. Parathyroid carcinoma 1%

7

Familial primary hyperparathyroidism
MEN1
MEN2A
Familail hypocalciuric hypercalcemia

1. MEN 1-inactivation of MEN1 gene on chromosome 11q13 (tumor suppressor gene)

2. MEN2A-activating mutation of RET (tyrosine kinase receptor) gene on chromosome 10q

3. familial hypocalciuric hypercalcemia-autosomal dominant disorder due to mutation in parathyroid calcium-sensing receptor gene (CASR) on chromosome 3

8

Parathyroid adenoma

Gross
-solitary
-increased uptake of radionuclide scan
.5-5 gm

Histology:
Sheets or nests of chief cells or oxyphil cells
Encapsulated lesion with compressed normal rim of parathyroid at pituitary
Mitotic figures rare
May find endocrine atypia-rep degenerative change-not a criteria for malignancy
-

9

Parathyroid hyperplasia

2-4 glands
combined weight 1 gm
microscopically diffuse or multinodular chief cell hyperplasia most common

10

Parathyroid carcinoma

Gross:
solitary mass, may exceed 10gm
-may be circumscribed lesion or clearly invasive neoplasm

Histo:
Cells resemble normal parathyroid and are arranged in trabeculae or nodules with dense fibrous capsule with intervening fibrous bands

Diagnosis: local invasive of surrounding tissue and metastasis

11

Osteitis fibrosa cystica

thinned bony cortex with marrow containing fibrous tissue, hemorrhages and cyst formation

12

Brown tumor

collection of osteoclasts, reactive giant cells and hemorrhage debris forming masses that stimulate tumor

13

Kidney changes from hyperparthyroidism

1. formation of stones
2. calcification of interstitium and tubules
3. metastatic calcification in organs like stomach, lung, myocardium or blood vessels

14

Primary Hyperparathyroidism
clinical manifestations

May be asymptomatic and identified by hypercalcemia on routine exam

bone, stones, groan, psychiatric undertones

15

Secondary Hyperparathyroidsim
Etiology

-process of chronic depression or decrease in calcium that causes compensatory overactivity of the parathyroid glands

--Renal Failure most common
1. decreased phosphate excretion-hyperphosphatemia-decreases serum calcium-parathyroid stimulation
2.deficiency of alpha1 hyodroxylase--deficiency of Vitamin D-less absorption of clcium from GI tract and eventually parathyroid stimulation

0ther eitologies-decreased dietary Ca, steatorrhea, vit D def

16

Secondary Hyperparathyroidsim
Clinical features

-skeletal changes not as severe as in primary hyperparathyroidism
-vascular calcification may cause significant ischemic damages to skin-calciphylaxis

17

Tertiary hyperparathyroidsim

MInority of patients-autonomous hyperparathyroidism with symptomatic hypercalcemia

-parathyroidectomy necessary for controlling symptoms

18

Hypoparathyroidism
Etiology

Less common than hyper
Etiology:
1. Surgically induced

2. Autoimmune
-mucocutaneous candidiasis
-adrenal insufficiency (autoimmune polyendocrine syndrome 1 APS1)

3. Autosomal dominant hypoparathyroidism-gain of function mutation in calcium sensing receptor gene (CASR)-hypercalcemia and hypocalcemia

4. Familial isolated hypoparathyroidism-rare disorder due to the encoding PTH precursor peptide

5. Congenital absence of parathyroid-DiGeorge or 22q11

19

Hypoparathyroidism CLinical manifestations

1. Tetany-numbness, paresthesias, carpopedal spasm, laryngospasm, seizures
2. chvostek sign-occude circulation in forearm, observe carpal spasm

3. mental status changes-emotional instability, anxiety, depression, confusion, hallucinations and frank psychosis

4. Intracranial manifestations-calcifications of basal ganglia, parkinson like movement disorders and increased intracranial pressure with papilledema

5. ocular disease-catarct formation

6. cardiovascular manifestation***************-Prolonged QT interval

7. Dental abnormalities-dental hypoplasia, failure of eruption, defective enamel and root formation and carious teeth

20

Pseudohypoparathyroidism

Rare disease due to end organ resistance to the actions of PTH
-increased to normal PTH with hypocalcemia