15.8 Parathyroid Gland

Question 1

What is the main cell of the PT gland and what is its function?

Answer 1

Chief Cell - regulate serum Ca2+ via PTH secretion

Question 2

What are the actions of PTH?

Answer 2

• Increased osteoclast action
• Increased small intestinal absorption of Ca2+
• Increased renal Ca2+ reabsorption and decreased Pi reabsorption

Question 3

How does PTH activate osteoclasts?

Answer 3

Indirectly via activation of the osteoblasts which will then activate the osteoclasts.

Question 4

Primary Hyperparathyroidism

Answer 4

Excess PTH due to a disorder of the PT gland

Question 5

What is the most common cause of primary hyperparathyroidism?

Answer 5

Parathyroid Adenoma

Question 6

Parathyroid Adenoma

Answer 6

Benign neoplasm usually involving one gland that often causes asymptomatic hypercalcemia

Question 7

How can hypercalcemia lead to acute pancreatitis?

Answer 7

Ca2+ is an enzyme activator which can activate the enzymes found in the pancreas

Question 8

What are the lab findings in primary hyperparathyroidism?

Answer 8

• Increased PTH
• Increased Ca2+
• Decreased Pi
• Increased cAMP in urine
• Increased alkaline phosphatase

Question 9

What is the treatment of parathyroid adenoma?

Answer 9

Surgical removal of the affected gland

Question 10

Secondary Hyperparathyroidism

Answer 10

Excess PTH due to disease process outside of the PT gland

Question 11

What is the most common cause of secondary hyperparathyroidism?

Answer 11

Chronic Renal Failure

Question 12

How does chronic renal failure lead to secondary hyperparathyroidism?

Answer 12

Decreased Pi excretion will lead to increased binding to free Ca2+ which leads to the stimulation of the PT glands

Question 13

What are the lab findings in secondary hyperparathyroidism?

Answer 13

• Increased PTH
• Decreased Ca2+
• Increased Pi
• Increased alkaline phosphatase

Question 14

What are the causes of hypoparathyroidism?

Answer 14

• Autoimmune
• Surgical Excision
• DiGeorge Syndrome

Question 15

What is the presentation of hypoparathyroidism?

Answer 15

• Low PTH and low Ca2+
• Muscle spasms
• Numbness and tingling

Question 16

Pseudohypoparathyroidism

Answer 16

End-organ resistance to PTH leading to hypocalcemia with increased PTH

Question 17

What is the autosomal dominant form of pseudohypoparathyroidism associated with?

Answer 17

Short stature and short 4th and 5th digits

Question 18

What is the molecular defect in pseudohypoparathyroidism?

Answer 18

Defect of the Gs signaling protein in the signal cascade responding to PTH