Hyperparathyroidism Lecture Notes

Overview

Hyperparathyroidism is characterized by high levels of parathyroid hormone (PTH). There are three types of hyperparathyroidism:

• Primary Hyperparathyroidism
• Secondary Hyperparathyroidism
• Tertiary Hyperparathyroidism

Understanding these types is crucial as they often cause confusion among medical students and doctors.

Physiology of Parathyroid Hormone

• The parathyroid glands are located on the four corners of the thyroid gland.
• Chief Cells in these glands produce parathyroid hormone (PTH) in response to low blood calcium levels.
• PTH increases blood calcium levels by:
  • Enhancing calcium absorption in the intestines.
  • Increasing calcium reabsorption in the kidneys, reducing urinary excretion.
  • Stimulating osteoclast activity in bones to release calcium.
• Vitamin D:
  • Produced in response to sunlight, also obtained through food or supplements.
  • Works alongside PTH to increase calcium absorption and is activated by PTH.
  • Deficiency can lead to low calcium levels.

Types of Hyperparathyroidism

Primary Hyperparathyroidism

• Cause: Uncontrolled PTH production due to a tumor in the parathyroid glands.
• Effects: Leads to hypercalcemia (high blood calcium levels).
• Treatment: Surgical removal of the tumor.

Secondary Hyperparathyroidism

• Causes:
  • Insufficient vitamin D.
  • Chronic renal failure.
• Effects:
  • Leads to hypocalcemia (low blood calcium levels).
  • Parathyroid glands increase PTH production to compensate.
  • Over time, gland hyperplasia occurs, increasing baseline PTH secretion.
• Serum Calcium Levels: Typically low or normal.
• Treatment:
  • Correcting vitamin D deficiency.
  • Renal transplant in chronic renal failure cases.

Tertiary Hyperparathyroidism

• Cause: Prolonged secondary hyperparathyroidism causing significant gland hyperplasia.
• Effects:
  • Persistent high PTH levels even after addressing secondary cause.
  • Results in hypercalcemia due to excessive calcium absorption.
• Treatment: Surgical removal of hyperplastic gland tissue.

Summary

• Primary Hyperparathyroidism: Tumor causes high PTH & high calcium; treated with surgery.
• Secondary Hyperparathyroidism: Caused by vitamin D deficiency or kidney disease; with high PTH & low/normal calcium; treated by addressing underlying causes.
• Tertiary Hyperparathyroidism: Result of prolonged secondary hyperparathyroidism, causing high calcium; treated by surgical removal of excess gland tissue.

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