2026 ICD-10-CM Diagnosis Code E21.3Hyperparathyroidism, unspecified

ICD-10-CM Codes›E00–E89›E20-E35›E21

ICD-10-CM E21.3
CMSSource: CMS FY 2026 ICD-10-CM dataset · Effective Oct 1, 2025 – Sep 30, 2026

E21.3 is a billable ICD-10-CM diagnosis code for hyperparathyroidism, unspecified. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 643 through 645. Coders also document this condition as brown tumor of hyperparathyroidism. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Other specified and unspecified endocrine disorders.

Code Identity

ICD-10-CM Code
E21.3
Billable Status
Yes — Valid for Submission
Code Describes
Hyperparathyroidism, unspecified
Short Description
Hyperparathyroidism, unspecified
Same as the full description in the CMS dataset.
Parent Code
E21
Hyperparathyroidism and other disorders of parathyroid gland

Code Classification

ChapterE00–E89Endocrine, nutritional and metabolic diseases
SectionE20-E35Disorders of other endocrine glands
CategoryE21Hyperparathyroidism and other disorders of parathyroid gland
This CodeE21.3Hyperparathyroidism, unspecified

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Brown tumor of hyperparathyroidism
  • Calcifying panniculitis due to hyperparathyroidism
  • Chronic kidney disease mineral and bone disorder
  • Endocrine myopathy
  • Hyperparathyroidism
  • Myopathy in hyperparathyroidism
  • Neonatal hyperparathyroidism
  • Renal osteodystrophy
  • Renal osteodystrophy due to hyperparathyroidism
  • Subcutaneous calcification

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

External Cause of Injuries IndexGuidance

References for this code in the External Cause of Injuries Index.

    • Arthritis, arthritic(acute) (chronic) (nonpyogenic) (subacute)
      • in (due to)
        • hyperparathyroidism NEC
    • Arthropathy
      • hemophilic NEC
        • in (due to)
          • hyperparathyroidism NEC
    • Hyperfunction
      • parathyroid (gland)
    • Hyperparathyroidism
    • Myopathy
      • in (due to)
        • hyperparathyroidism NEC

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR END015
Other specified and unspecified endocrine disorders
Default principal diagnosis: inpatient Yes · outpatient Yes

Clinical InformationClinical

  • Hyperparathyroidism

    a condition of abnormally elevated output of parathyroid hormone (or pth) triggering responses that increase blood calcium. it is characterized by hypercalcemia and bone resorption, eventually leading to bone diseases. primary hyperparathyroidism is caused by parathyroid hyperplasia or parathyroid neoplasms. secondary hyperparathyroidism is increased pth secretion in response to hypocalcemia, usually caused by chronic kidney diseases.

  • Hyperparathyroidism, Primary

    a condition of abnormally elevated output of parathyroid hormone due to parathyroid hyperplasia or parathyroid neoplasms. it is characterized by the combination of hypercalcemia, phosphaturia, elevated renal 1,25-dihydroxyvitamin d3 synthesis, and increased bone resorption.

  • Hyperparathyroidism, Secondary

    abnormally elevated parathyroid hormone secretion as a response to hypocalcemia. it is caused by chronic kidney failure or other abnormalities in the controls of bone and mineral metabolism, leading to various bone diseases, such as renal osteodystrophy.

Patient EducationClinical

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.

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert E21.3 to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
252.00 Hyperparathyroidism NOS
Exact Match The mapping is direct, with no qualifiers.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2025No changes
FY 2026CurrentCurrent code set, no changesEffective October 1, 2025 through September 30, 2026.

Questions About E21.3Overview

Is E21.3 (Hyperparathyroidism and other disorders of parathyroid gland) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report hyperparathyroidism, unspecified on HIPAA-covered claims from October 1, 2025 through September 30, 2026.

What MS-DRG does E21.3 group to?

When hyperparathyroidism, unspecified is the principal diagnosis on an inpatient stay, it groups to MS-DRG 643, 644, 645, with relative weights from 0.7683 to 1.6461 depending on complications. Higher weights mean higher Medicare reimbursement.

What is the ICD-9 equivalent of E21.3?

Under the General Equivalence Mappings, hyperparathyroidism, unspecified converts to ICD-9-CM 252.00 (hyperparathyroidism NOS). The mapping is a direct match.

Footnotes

[1] Chronic - a chronic condition code indicates a condition lasting 12 months or longer and its effect on the patient based on one or both of the following criteria:

  • The condition results in the need for ongoing intervention with medical products,treatment, services, and special equipment
  • The condition places limitations on self-care, independent living, and social interactions.