Disorders of Parathyroid glands Flashcards
from where is the parathyroid derived?
from the third and fourth branchial pouches.
how many parathyroid glands are there?
what cells compose the parathyroid gland?
4
oxyphil and chief cells
what do chief cells synthesize?
PTH
what are the functions of PTH?
- Activates osteoclasts (mobilizes Ca from bone)
- Increases resorption of calcium from renal tubules.
- Increases the conversion of vitamin D to its active form.
- Increases Ca absorption from GIT.
1. Increases urinary phosphate excretion.
how does PTH maintain ionized calcium levels in blood?
- Increases bone resorption and
- Renal and GIT resorption of calcium
PTH secretion is controlled by what?
Level of free ionized calcium in blood stream
- PTH secretion stimulated by hypocalcemia
- PTH secretion suppressed by hypercalcemia
what does Total Serum calcium represent?
bound calcium + free calcium
what is the activated form of calcium?
free calcium
What are the effect of hypoalbuminemia on calcium levels?
- Causes decreased total serum calcium
- Due to a decrease in Ca bound to albumin.
- Normal free Ca levels, normal PTH
- No evidence of tetany**.
what is the effect of respiratory or metabolic alkalosis on calcium levels?
- Alkalosis increases negative charges on albumin.
- Extra negative charges bind some of the free Ca
- Total serum calcium remains normal
- Decreased free calcium, increased PTH
- Patient develops tetany**
who secretes Calcitonin?
what stimulates the synthesis of calcitonin?
C cells of thyroid
hypercalcemia
what are the actions of calcitonin?
- Inhibits bone resorption by inhibiting the activity of osteoclasts.
- Inhibits absorption of calcium from intestine.
- Net effect = decreased calcium levels
what are the 2 Disorders of Parathyroid glands?
- Hyperparathyroidism
- Hypoparathyroidism
Hyperparathyroidism (HPTH) can divide into 2 types?
- Primary Hyperparathyroidism
- Secondary Hyperparathyroidism
Primary hyperparathyroidism is characterized by what?
usually affects who?
Unregulated overproduction* of PTH by the parathyroid leading to hypercalcemia.
50 y/o women
what are the 2 types of primary hyperparathyroidism?
sporadic
associated with MEN I or II
what is a Parathyroid adenoma’s gross findings?
which parathyroid gland is usually affected
A benign tumor, Solitary & well circumscribed.
Right inferior parathyroid gland is most often involved
what are the parthyroid glands micro findings?
- Composed of sheets of chief cells with no intervening fat.
- Remainder of the gland plus all other glands show atrophy.
- due to suppression of PTH by hypercalcemia.
what is this test called?
what is it showing?
parathyroid Tc99 scan
parathyroid adenoma
how many glands are affected by primary parathyroid hyperplasia?
what are the micro findings?
all 4 glands
chief cell hyperplasia with sparse fat tissue.
what is this showing?
parathyroid hyperplasia
most cases of hyperparathyroidism are?
asymptomatic and found incidentally
what are the Primary Hyperparathyroidism Renal Clinical findings?
- Calcium oxalate stones = nephrolithiasis (most common presentation**)
- Nephrocalcinosis (causes polyuria and renal failure).
what are the Primary Hyperparathyroidism GIT Clinical findings?
- Peptic ulcer disease: calcium stimulates gastrin release which increases gastric acid.
- Acute pancreatitis: calcium activates phospholipases
- Constipation: Most common** GI complaint (hypomotility)
what are the Primary Hyperparathyroidism Bones Clinical findings?
what will you see in micro findings?
Osteitis Fibrosa Cystica
- Cystic and hemorrhagic bone lesion
- Caused by increased osteoclastic activity
- Commonly involves the jaw and fingers
Aggregates of osteoclasts, reactive giant cells and hemorrhage mimicking neoplasm.
Called the “brown tumor” of hyperparathyroidism
What are the Primary Hyperparathyroidism Eye Clinical findings?
- Band keratopathy in the limbus of the eye
- Due to Metastatic calcifications
What are the Primary Hyperparathyroidism CVS Clinical findings?
- Diastolic hypertension
- calcium increases muscular contraction in the peripheral resistance vessels.
What are the Primary Hyperparathyroidism CNS Clinical findings?
Depression and seizures (Metastatic calcification)
what are the Laboratory findings found in Primary HyperParaThyroidism?
- Increased serum PTH
- Increased serum calcium = hypercalcemia
- Decreased serum phosphate = hypophosphatemia
what is this showing?
parathyroid hyperplasia
what are the Primary Hyperparathyroidism GIT Clinical findings?
- Peptic ulcer disease: calcium stimulates gastrin release which increases gastric acid.
- Acute pancreatitis: calcium activates phospholipases
- Constipation: Most common** GI complaint (hypomotility)
how does Malignancy induced hypercalcemia happen?
- Bone metastasis with activation of osteoclasts
- Ectopic secretion of PTH related protein (SCC of lung, RCC)
- Multiple myeloma: ↑ secretion of osteoclast activating factor (IL-1) by plasma cells.
how does Sarcoidosis happen?
Macrophages in granuloma synthesize 1 alpha hydroxylase, causing Hypervitaminosis D
what is the most common cause of secondary hyperparathyroidism?
chronic renal failure
what do you see in the labs for 2ry hyperparathyroidism?
Decreased calcium, increased PTH, increased phosphate.
what is Primary hypoparathyroidism?
Refers to hypofunction of parathyroid gland leading to hypocalcemia.
what is the etiology of 1ry hypoparathyroidsm?
- Previous thyroid surgery (most common cause)
- Di George syndrome: congenital absence of parathyroid glands
- Autoimmune hypoparathyroidism
- Hypomagnesemia: required for PTH activation
PTHrP is always made by ?
the tumor, not the body
Reduction in total and ionized calcium levels in 1ry hypoparathyroidism results in what?
- Tetany
- Calcification of basal ganglia
- Due to metastatic calcification
- Increased phosphorus drives Ca into brain
- Cataracts
- Candida infection (?cause)
- Prolonged QT interval
why does tetany happen in 1ry hypoparathyroidism?
due to decreased ionized calcium.
- Decreased ionized Ca causes partial depolarization of nerve and muscle
A smaller stimulus is required to initiate an action potential.
what 2 signs can you find in 1ry hypoparathyroidism?
- Carpopedal spasm: thumb flexes into palm
- Chovestek’s sign: facial twitch after tapping the facial nerve.
what Laboratory findings are indicative of 1ry hypoparathyroidism?
- Low PTH
- Hypocalcemia
- Hyperphosphatemia
what is Pseudohypoparathyroidism?
Sex linked inherited disease.
Characterized by end organ resistance (kidney) to PTH.
what do patients with pseudohypoparathyroidism have?
- Mental retardation
- Calcification of basal ganglia
- Short 4th and 5th metacarpals** (knuckle-knuckle- dimple – dimple sign)
- Short stature and other skeletal abnormalities.
what are the lab findings in pseudohypoparathyroidism?
Hypocalcemia, hyperphosphatemia and normal or high PTH.
what are 4 other causes of hypocalcemia?
- Acute pancreatitis: Calcium bound to fatty acids in enzymatic fat necrosis.
- Hypovitaminosis D: Chronic renal failure: MCC
- Hypoalbuminemia: MCC of hypocalcemia
- Hypomagnesemia
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