E21.0 — Primary hyperparathyroidism
E21.0 is a billable, specific ICD-10-CM code for primary hyperparathyroidism. It is valid for submission on a claim.
Inclusion terms
Alternative wordings a physician may use in the chart for this same code.
- Hyperplasia of parathyroid
- Osteitis fibrosa cystica generalisata [von Recklinghausen's disease of bone]
Excludes1 inherited from the categories above E21.0
These are not written on E21.0, but they bind it: a note on a category applies to every code beneath it. Billing E21.0 with anything listed here is a denial.
Excludes2 inherited from the categories above E21.0
Also inherited, and the opposite of Excludes1: these conditions are not part of E21.0, but a patient can have both, so you may code both.
Other codes that can never be billed with E21.0
These codes carry an Excludes1 note pointing at E21.0. The conflict binds both ways, but ICD-10-CM only writes it down on one side — so you would not find this by reading E21.0 alone.
Risk adjustment
E21.0 does not map to an HCC and does not risk-adjust under CMS-HCC V28. That is normal — most ICD-10 codes do not. It still needs to be coded correctly; it just will not move a RAF score.
Medicare coverage
E21.0 is named in 17 Medicare coverage policies — 17 listing it as supporting medical necessity. Which of them applies to you depends on your Medicare contractor, and coverage genuinely differs by state.
- A56416Billing and Coding: Assays for Vitamins and Metabolic Function
- A56798Billing and Coding: Vitamin D Assay Testing
- A56841Billing and Coding: Vitamin D; 25 hydroxy, includes fraction(s), if performed
- A57122Billing and Coding: Parathormone (Parathyroid Hormone)
How E21.0 is indexed
Coders do not find codes by browsing the tabular list — they look them up in the alphabetic index, under the word the physician wrote. These are the index entries that lead here, so you can see which chart wordings map to E21.0.
- Disease, diseased›osteofibrocystic
- Enlargement, enlarged›parathyroid(gland)
- Hyperparathyroidism›primary
- Hyperplasia, hyperplastic›parathyroid(gland)
- Hypertrophy, hypertrophic›parathyroid(gland)
- Osteitis›parathyroid
- Recklinghausen disease›bones
- Osteitis›fibrosa NEC›cystica(generalisata)
- Osteitis›fibrosa NEC›osteoplastica
- Von Recklinghausen›disease›bones
- Curvature›spine›due to or associated with›osteitis›fibrosa cystica
Code history
E21.0 has not changed since FY2024 — no addition, revision or deletion across the three most recent ICD-10-CM releases.
Related codes at this level
Codes that share E21. If E21.0 is not quite right, the correct code is usually one of these.
Questions about E21.0
- Is E21.0 a billable ICD-10-CM code?
- Yes. E21.0 is a billable, specific ICD-10-CM code and is valid for submission on a claim.
- Where does E21.0 sit in the tabular list?
- Endocrine, nutritional and metabolic diseases (E00-E89), in the block Disorders of other endocrine glands (E20-E35).
- What cannot be coded together with E21.0?
- E21.0 carries Excludes1 notes, which means the conditions they list can never be coded together with it on the same encounter. Some are written on the categories above E21.0 (E21) and apply to it just the same.