Medical Health Encyclopedia

Secondary hyperparathyroidism

Injury Disease Nutrition Poison Symptoms Surgery Test Special Topic

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Endocrine glands

Overview Symptoms Treatment Prevention

Secondary hyperparathyroidism

Definition:

The parathyroids are four glands in the neck that produce parathyroid hormone to help control calcium metabolism.

Causes, incidence, and risk factors:

Text Continues Below

---

Parathyroid hormone helps maintain blood calcium by regulating bone turnover, absorption of calcium from the gut, and excretion of calcium in the urine.

Many disorders may lead to secondary hyperparathyroidism by causing hypocalcemia (low levels of calcium in the blood), disordered phosphate balance, or both. These include the following:

• Disorders of vitamin D
  • Rickets (osteomalacia)
  • Vitamin D deficiency
  • Vitamin D malabsorption
  • Abnormal vitamin D metabolism induced by drugs

At-risk populations include children with malnutrition and elderly people with little sun exposure.

• Disorders of phosphate metabolism
  • Malnutrition
  • Malabsorption
  • Aluminum toxicity
  • Kidney disease
  • Some types of cancer
  • Phosphate depletion (may also cause osteomalacia)
• Calcium deficiency
  • Not enough calcium in the diet
  • Too much calcium loss in the urine
• Chronic renal failure

Chronic renal failure is an important cause of secondary hyperparathyroidism. The disorder is complex:

• Phosphate clearance is impaired.
• Phosphate is released from bone.
• Vitamin D is not produced.
• Intestinal calcium absorption is low.
• Blood levels of calcium are lowered.

A positive feedback loop leads to increased bone resorption (bone is broken down in an attempt to regulate abnormal levels of these chemicals) and hyperphosphatemia (high levels of phosphates in the blood), which causes further secondary hyperparathyroidism.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org). The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed physician should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. Copyright 2004 A.D.A.M., Inc. Any duplication or distribution of the information contained herein is strictly prohibited.