What is a Chief cell in the parathyroid gland?
Cells that regulate serum free (ionized) calcium via parathyroid hormone secretion
What are actions of PTH?
- INCREASE bone osteoclast activity to release Ca and Phosphate (by activating osteoblasts to release RANKL)
- INCREASE in small bowel absorption of Ca and Phosphate
- INCREASE renal Ca reabsorption and
DECREASE phosphate reabsorption
What is Primary Hyperparathyroidism?
Excess PTH due to disorder of parathyroid gland
Parathyroid Adenoma (*Most Common* >80%)
What is a parathyroid adenoma?
Benign neoplasm, usually involving one gland
- Most often results in asymptomatic hypercalcemia
What are symptoms of Primary Hyperparathyroidism?
Any symptoms are consequences of Increased PTH and hypercalcemia:
- Nephrocalcinosis (metastatic calcification of tubules of kidney)
- CNS disturbances: depression, seizures
- Constipation, peptic ulcer disease, acute pancreatitis (Ca activates enzymes in pancreas)
- Osteitis fibrosa cystica
What are the lab findings in Primary Hyperparathyroidism?
Increased serum PTH
Increased serum Ca
Decreased serum Phosphate
Increased urinary cAMP (PTH --> Gs coupled receptor --> activation of adenylate cyclase --> increased cAMP)
Increased serum ALP (makes alkaline environment for bone to be layed down, it's a sign of the osteoblastic activity)
What is treatment of PHP?
Surgical removal of affected gland
What is secondary hyperparathyroidism?
Excess production of PTH due to disease process extrinsic to the parathyroid gland
- Most common cause is chronic renal failure
How does renal failure lead to secondary hyperparathyroidism?
Renal insufficiency --> Decreased phosphate excretion --> Increased serum phosphate binds free calcium --> Decreased free calcium stimulates all four parathyroid glands --> increased PTH leads to bone resorption
What are the lab findings of Secondary
Decreased serum Ca
Increased serum phosphate
Increased alkaline phosphatase
What is hypoparathyroidism? Causes?
- Causes include:
What are the clinical features of hypoparathyroidism?
Numbness and tingling (especially around the lips)
Muscle spasms (tetany) - Trousseau and Chvostek's signs
Decreased serum Ca
What is pseudohypoparathyroidism?
Signs and symptoms of hypoparathyroidism, but not due to decreased PTH
--> Due to end-organ resistance to PTH often due to defect in Gs protein's ability to turn on adenylate cyclase
Leads to hypocalceia with increased PTH levels
--> Autosomal dominant form is associated with short stature and short 4th and 5th digits