E21.0 - Primary hyperparathyroidism

Version 2023
ICD-10:E21.0
Short Description:Primary hyperparathyroidism
Long Description:Primary hyperparathyroidism
Status: Valid for Submission
Version:ICD-10-CM 2023
Code Classification:
  • Endocrine, nutritional and metabolic diseases (E00–E90)
    • Disorders of other endocrine glands (E20-E35)
      • Hyperparathyroidism and other disorders of parathyroid gland (E21)

E21.0 is a billable ICD-10 code used to specify a medical diagnosis of primary hyperparathyroidism. The code is valid during the fiscal year 2023 from October 01, 2022 through September 30, 2023 for the submission of HIPAA-covered transactions.

Approximate Synonyms

The following clinical terms are approximate synonyms or lay terms that might be used to identify the correct diagnosis code:

Clinical Information

Tabular List of Diseases and Injuries

The Tabular List of Diseases and Injuries is a list of ICD-10 codes, organized "head to toe" into chapters and sections with coding notes and guidance for inclusions, exclusions, descriptions and more. The following references are applicable to this diagnosis code:


Inclusion Terms

Inclusion Terms
These terms are the conditions for which that code is to be used. The terms may be synonyms of the code title, or, in the case of "other specified" codes, the terms are a list of the various conditions assigned to that code. The inclusion terms are not necessarily exhaustive. Additional terms found only in the Alphabetic Index may also be assigned to a code.

Index to Diseases and Injuries References

The Index to Diseases and Injuries is an alphabetical listing of medical terms, with each term mapped to one or more ICD-10 code(s). The following references for this diagnosis code are found in the injuries and diseases index:

Convert to ICD-9 Code

Source ICD-10 CodeTarget ICD-9 Code
E21.0252.01 - Primary hyperparathyroid

Patient Education


Parathyroid Disorders

Most people have four pea-sized glands, called parathyroid glands, on the thyroid gland in the neck. Though their names are similar, the thyroid and parathyroid glands are completely different. The parathyroid glands make parathyroid hormone (PTH), which helps your body keep the right balance of calcium and phosphorous.

If your parathyroid glands make too much or too little hormone, it disrupts this balance. If they secrete extra PTH, you have hyperparathyroidism, and your blood calcium rises. In many cases, a benign tumor on a parathyroid gland makes it overactive. Or, the extra hormones can come from enlarged parathyroid glands. Very rarely, the cause is cancer.

If you do not have enough PTH, you have hypoparathyroidism. Your blood will have too little calcium and too much phosphorous. Causes include injury to the glands, endocrine disorders, or genetic conditions. Treatment is aimed at restoring the balance of calcium and phosphorous.

NIH: National Institute of Diabetes and Digestive and Kidney Diseases


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Familial isolated hyperparathyroidism

Familial isolated hyperparathyroidism is an inherited condition characterized by overactivity of the parathyroid glands (hyperparathyroidism). The four parathyroid glands are located in the neck, and they release a hormone called parathyroid hormone that regulates the amount of calcium in the blood. In familial isolated hyperparathyroidism, one or more overactive parathyroid glands release excess parathyroid hormone, which causes the levels of calcium in the blood to rise (hypercalcemia). Parathyroid hormone stimulates the removal of calcium from bone and the absorption of calcium from the diet, and the mineral is then released into the bloodstream.

In people with familial isolated hyperparathyroidism, the production of excess parathyroid hormone is caused by tumors that involve the parathyroid glands. Typically only one of the four parathyroid glands is affected, but in some people, more than one gland develops a tumor. The tumors are usually noncancerous (benign), in which case they are called adenomas. Rarely, people with familial isolated hyperparathyroidism develop a cancerous tumor called parathyroid carcinoma. Because the production of excess parathyroid hormone is caused by abnormalities of the parathyroid glands, familial isolated hyperparathyroidism is considered a form of primary hyperparathyroidism.

Disruption of the normal calcium balance resulting from overactive parathyroid glands causes many of the common signs and symptoms of familial isolated hyperparathyroidism, such as kidney stones, nausea, vomiting, high blood pressure (hypertension), weakness, and fatigue. Because calcium is removed from bones to be released into the bloodstream, hyperparathyroidism often causes thinning of the bones (osteoporosis). The age at which familial isolated hyperparathyroidism is diagnosed varies from childhood to adulthood. Often, the first indication of the condition is elevated calcium levels identified through a routine blood test, even though the affected individual may not yet have signs or symptoms of hyperparathyroidism or hypercalcemia.


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Primary Hyperparathyroidism

Describes symptoms, causes, and treatment of primary hyperparathyroidism where one or more enlarged parathyroid gland secretes too much parathyroid hormone.
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Code History