Krafts: Parathyroid Pathology Flashcards
Where do the upper parathyroids come from?
FOURTH pharyngeal pouch>
descend w/ the thyroid
Where do the lower parathyroids come from?
THIRD pharyngeal pouch>
descend w/ the thymus
The first groove/cleft forms the…
ear stuff
What cells are associated w/ the parathyroid gland?
chief cells
oxyphil cells
What does PTH do?
INCREASES serum Ca:
bone resorption renal reabsorption of calcium renal excretion of phosphate renal conversion of vitamin D to its active form gut absorption of calcium
What is the purpose of Vit D?
Stimulates gut to absorb calcium, phosphorus
Helps PTH to get calcium out of bone
Stimulates kidney to reabsorb calcium
Where do you metabolize vit D?
liver (25 hydroxylase)
kidney (a-1 hydroxuylase)–> active form
What controls PTH release?
FREE Ca
Decreased Ca> increased PTH synthesis/release
Increased Ca> decreased PTH synthesis/release
What causes hypercalcemia?
- Hyperparathyroidism
- Malignancy***–>impt to rule out if a pt comes in w/ hypercalcemia
- Metastases
- PTH-related protein - Vitamin D overdose
- Thiazide diuretics
- Milk-alkali syndrome (drink a lot of milk and eat a lot of tums)
What is the MC cause of SYMPTOMATIC hypercalcemia?
malignancy
What is the MC cause of asymptomatic hypercalcemia?
Hyperparathyroidism
What is primary hyperparathyroidism?
hyperparathyroidism d/t a parathyroid problem
What causes primary hyperparathyroidism?
Parathyroid adenoma**MC
Parathyroid hyperplasia
Parathyroid carcinoma
What are signs of primary hyperparathyroidism?
Very common and often asymptomatic!
Stone: kidney stones, other stones
Bone: pain, brown tumors, worse
Groan: gastrointestinal problems
Moan: mental changes
What is the mechanism of primary hyperparathyroidism?
Increased PTH>
gut absorbs more Ca/bone gives up more Ca>
ELEVATED serum Ca
What lab findings are associated with primary hyperparathyroidism?
Increased PTH and serum Ca
Decreased phosphate (inverse of Ca)
What does PTH affect bone?
Osteoclast activation (chewed up) Osteoblast activation (build up) Brown tumors Osteitis fibrosa cystica (severe case of brown tumors and hypercalcemia)
What are RANKL and M-DSF?
RANKL (ligand on osteoblast)>
RANK receptor on osteoclast precursor>
stimulates osteoclast to chew up bone
(same thing with M-CSF:M-CSFr)
What is the MC cause of primary hyperparthyroidism?
Parathyroid adenoma
SOLITARY
What genetic defects are associated w/ PT Adenoma?
PRAD 1 overexpression
MEN 1 loss or mutation (multiple endocrine neoplasia syndrome)
What is PT hyperplasia?
less common
usually affects all 4 glands
most sporadic
What is a rare cause of primary hyper PT?
parathyroid carcinoma
Sxs: abrupt onset of bone pain, usually well differentiated tumor w/ a POOR prognosis
What is secondary HPT?
hyperparathyroidism d/t chronic hypocalcemia
What causes secondary HPT?
Renal failure (most cases)** Diet poor in calcium Vitamin D deficiency
