2025 ICD-10-CM Diagnosis Code E21.0

Primary hyperparathyroidism

• E21.0 is a billable/specific ICD-10-CM code that can be used to indicate a diagnosis for reimbursement purposes.
• The 2025 edition of ICD-10-CM E21.0 became effective on October 1, 2024.
• This is the American ICD-10-CM version of E21.0 – other international versions of ICD-10 E21.0 may differ.

Applicable To

• Hyperplasia of parathyroid
• Osteitis fibrosa cystica generalisata [von Recklinghausen’s disease of bone]

The following code(s) above E21.0 contain annotation back-references

 that may be applicable to E21.0:

• E00-E89  Endocrine, nutritional and metabolic diseases
• E20-E35  Disorders of other endocrine glands
• E21  Hyperparathyroidism and other disorders of parathyroid gland

Approximate Synonyms

• Hyperparathyroidism, primary
• Parathyroid hyperplasia

Clinical Information

• 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.
• Abnormal increase in the number of otherwise normal cells in the parathyroid gland without tumor formation that leading to enlargement of the gland; it differs from hypertrophy, which is an increase in bulk without an increase in the number of cells.
• Hyperfunction of the parathyroid glands resulting in the overproduction of parathyroid hormone. It is caused by parathyroid adenoma, parathyroid hyperplasia, parathyroid carcinoma, and multiple endocrine neoplasia. It is associated with hypercalcemia and hypophosphatemia. Signs and symptoms include weakness, fatigue, nausea, vomiting, constipation, depression, bone pain, osteoporosis, cystic bone lesions, and kidney stones.

ICD-10-CM E21.0 is grouped within Diagnostic Related Group(s) (MS-DRG v42.0):

• 643 Endocrine disorders with mcc
• 644 Endocrine disorders with cc
• 645 Endocrine disorders without cc/mcc

Convert E21.0 to ICD-9-CMCode History

• 2016 (effective 10/1/2015): New code (first year of non-draft ICD-10-CM)
• 2017 (effective 10/1/2016): No change
• 2018 (effective 10/1/2017): No change
• 2019 (effective 10/1/2018): No change
• 2020 (effective 10/1/2019): No change
• 2021 (effective 10/1/2020): No change
• 2022 (effective 10/1/2021): No change
• 2023 (effective 10/1/2022): No change
• 2024 (effective 10/1/2023): No change
• 2025 (effective 10/1/2024): No change

Code annotations containing back-references to E21.0:

• Code First: G73.7, M49
• Type 1 Excludes: E83.5, M85.6

Diagnosis Index entries containing back-references to E21.0:

• Curvature
  • spine (acquired) (angular) (idiopathic) (incorrect) (postural) – see Dorsopathy, deforming
    • due to or associated with
      • osteitis
        • fibrosa cystica E21.0 – see also subcategory M49.8
• Disease, diseased – see also Syndrome
  • osteofibrocystic E21.0
• Enlargement, enlarged – see also Hypertrophy
  • parathyroid E21.0 (gland)
• HyperparathyroidismE21.3
  • primary E21.0
• Hyperplasia, hyperplastic
  • parathyroid E21.0 (gland)
• Hypertrophy, hypertrophic
  • parathyroid E21.0 (gland)
• Osteitis – see also Osteomyelitis
  • fibrosa NEC – see Cyst, bone, by site
    • cystica E21.0 (generalisata)
    • osteoplastica E21.0
  • parathyroid E21.0
• Recklinghausen diseaseQ85.01
  • bones E21.0
• Von Recklinghausen
  • disease (neurofibromatosis) Q85.01
    • bones E21.0