15.8 Parathyroid Glands Flashcards
Which cells regulate serum free (ionized) calcium via PTH secretion?
Chief cells (in the parathyroid)
What are the three effects of PTH secretion?
- increases bone osteoclast activity, releasing calcium and phosphate
- activates vitamin D –> increased small bowel absorption of calcium and phosphate
- increases renal calcium reabsorption (DCT) and DECREASES phosphate reabsorption (PCT)
What is primary hyperparathyroidism?
excess PTH due to a disorder of the parathyroid gland itself
What is the most common cause of primary hyperparathyroidism?
Parathyroid adenoma (sporadic parathyroid hyperplasia and parathyroid carcinoma are less common)
Parathyroid adenoma most often results in asymptomatic
hypercalcemia
5 possible symptoms of parathyroid adenoma
- Nephrolithiasis
- Nephrocalcinosis (metastatic calcification of renal tubules)
- CNS disturbances
- constipation, peptic ulcer dz, acute pancreatitis
- osteitis fibrosa cystica
lab finding of primary hyperparathyroidism
Increased serum PTH, calcium, alkaline phosphatase, and urinary cAMP
Decreased serum phosphate
How do you treat primary hyperparathyroidism?
surgical removal of the affected gland
what is secondary hyperparathyroidism
excess production of PTH due to a disease process extrinsic to the parathyroid gland.
What is the most common cause of secondary hyperparathyroidism?
chronic renal failure
How does chronic renal failure lead to lead to secondary hyperparathyroidism?
renal insufficiency –> decreased phosphate excretion –> increased serum phosphate (binds free calcium) –> decreased free calcium –> increased PTH –> bone resorption –> renal osteodystrophy
lab findings of secondary hyperparathyroidism secondary to chronic renal failure
Increased serum PTH, phosphate, and alkaline phosphatase
Decreased serum calcium
Why is there increased serum alkaline phosphatase in secondary hyperparathryoidism?
reflects osteoBLAST activity (necessary to activate osteoclasts)
what is hypoparathyroidism?
low PTH
name three causes of hypoparathyroidism
- AI damage to parathyroids
- surgical excision (botched thyroidectomy)
- DiGeorge syndrome
two symptoms of hypoparathyroidism –> hypocalcemia
- numbness and tingling (circumoral)
2. muscle spasms (tetany)
what do you call tetany that can be elected with filling of a BP cuff?
Trousseau sign (hypocalcemia
what do you call tetany that can be elicited with tapping on the facial nerve?
Chvostek sign
Labs of hypoparathyroidism
decreased PTH and calcium
What is pseudohypoparathyroidism?
end-organ resistance to PTH
labs of pseudohypoparathyroidism?
Increased PTH and decreased calcium
differentiate pseudo and regular hypoparathyroidism by labs
pseudo - increased PTH
normal - decreased PTH
(both have low calcium)
what causes the autosomal dominant form of pseudohypoparathyroidism?
Gs mutation
AD pseudohypoparathyroidism is associated with
short stature and short 4th and 5th digits
