Pathology: Parathyroid II

Question 1

What is a Chief cell in the parathyroid gland?

Answer 1

Cells that regulate serum free (ionized) calcium via parathyroid hormone secretion

Question 2

What are actions of PTH?

Answer 2

• 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**

Question 3

What is Primary Hyperparathyroidism?

Answer 3

Excess PTH due to disorder of parathyroid gland

Examples:
Parathyroid Adenoma (*Most Common* >80%)
Sporadic hyperplasia
Parathyroid Carcinoma

Question 4

What is a parathyroid adenoma?

Answer 4

Benign neoplasm, usually involving one gland

• Most often results in asymptomatic hypercalcemia

Question 5

What are symptoms of Primary Hyperparathyroidism?

Answer 5

Usually Asymptomatic

Any symptoms are consequences of Increased PTH and hypercalcemia:

• *- Nephrolithiasis**
• *- 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**

Question 6

What are the lab findings in Primary Hyperparathyroidism?

Answer 6

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)

Question 7

What is treatment of PHP?

Answer 7

Surgical removal of affected gland

Question 8

What is secondary hyperparathyroidism?

Answer 8

Excess production of PTH due to disease process extrinsic to the parathyroid gland

• Most common cause is chronic renal failure

Question 9

How does renal failure lead to secondary hyperparathyroidism?

Answer 9

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

Question 10

What are the lab findings of Secondary
Hyperparathyroidism?

Answer 10

Increased PTH

Decreased serum Ca

Increased serum phosphate

Increased alkaline phosphatase

Question 11

What is hypoparathyroidism? Causes?

Answer 11

Low PTH

• Causes include:
  Autoimmune damage
  Surgical excision
  DiGeorge syndrome

Question 12

What are the clinical features of hypoparathyroidism?

Answer 12

Numbness and tingling (especially around the lips)

Muscle spasms (tetany) - Trousseau and Chvostek’s signs

Decreased PTH

Decreased serum Ca

Question 13

What is pseudohypoparathyroidism?

Answer 13

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