ICD-10 E21.0
Billable / Specific HCC v28: 23Primary hyperparathyroidism
About ICD-10-CM E21.0
ICD-10-CM code E21.0 represents Primary hyperparathyroidism. This is a billable/specific code in the Endocrine, Nutritional, and Metabolic chapter (block E21). The 2026 edition of ICD-10-CM E21.0 became effective on October 1, 2025.
Coding Tips for E21.0
Specialist guidance from the PayerReady Medical Coding Team. Specificity warnings, HCC capture rules, sequencing notes.
E21.0 is a CMS-HCC v28 risk-adjustment code (category 23). To count for the patient Risk Adjustment Factor (RAF), document the diagnosis with MEAT language each calendar year: Monitored, Evaluated, Assessed, Treated. A diagnosis on the problem list alone does not satisfy CMS RADV audit standards. Include the diagnosis in the assessment with current status and current treatment plan.
Inclusion Terms / Approximate Synonyms
Clinical terms and conditions classified under E21.0. Per CMS ICD-10-CM Tabular 2026.
- Hyperplasia of parathyroid
- Osteitis fibrosa cystica generalisata [von Recklinghausen's disease of bone]
Medicare Advantage HCC Impact
Capture this diagnosis annually for accurate risk adjustment. Missed HCC captures are the #1 revenue leak in Medicare Advantage risk programs.
Medicare LCD Coverage for E21.0
Local Coverage Determinations (LCDs) from CMS MACs that list E21.0 as a covered diagnosis.
Showing top 10 of 102 total . Click a CPT for full coverage scope.
Commercial Payer Coverage
Coverage policies from major commercial payers referencing E21.0.
2 Cigna
5 Medicare
CPT Codes Commonly Billed with E21.0
Procedures frequently paired with this diagnosis based on PayerReady's Dx↔Px linkage data.
- 77081 CMS LCD: Billing and Coding: Bone Mass Measurement CMS LCD
- 0556T CMS LCD: Billing and Coding: Bone Mass Measurement CMS LCD
- 78350 CMS LCD: Billing and Coding: Bone Mass Measurement CMS LCD
- 0554T CMS LCD: Billing and Coding: Bone Mass Measurement CMS LCD
- 77085 CMS LCD: Billing and Coding: Bone Mass Measurement CMS LCD
- 0558T CMS LCD: Billing and Coding: Bone Mass Measurement CMS LCD
- 0555T CMS LCD: Billing and Coding: Bone Mass Measurement CMS LCD
- 0557T CMS LCD: Billing and Coding: Bone Mass Measurement CMS LCD
- 77078 CMS LCD: Billing and Coding: Bone Mass Measurement CMS LCD
- 76977 CMS LCD: Billing and Coding: Bone Mass Measurement CMS LCD
Convert E21.0 to ICD-9-CM
Per CMS General Equivalence Mappings (GEMs), useful for legacy data review and historical claim analysis.
| ICD-10 | ICD-9 | Mapping Flags |
|---|---|---|
| E21.0 | 25201 | 00000 |
Flags format (5 digits): Approximate · No Map · Combination · Scenario · Choice List. Source: CMS 2017 GEMs (final version).
Codes Adjacent To E21.0
Other codes in section E20-E35 (Disorders of other endocrine glands).
ICD-10 E21.0, Billing FAQ
Is ICD-10 code E21.0 billable? +
Yes, E21.0 is a billable ICD-10-CM code that can appear as a primary or secondary diagnosis on claims.
What other names or terms map to E21.0? +
ICD-10 E21.0 includes: Hyperplasia of parathyroid; Osteitis fibrosa cystica generalisata [von Recklinghausen's disease of bone].
Does E21.0 affect Medicare Advantage HCC risk adjustment? +
Yes. E21.0 maps to CMS-HCC v28 category 23. Capture this diagnosis annually for accurate Medicare Advantage risk score.
What CPT codes are commonly billed with E21.0? +
Procedures frequently paired with E21.0 include: 77081, 0556T, 78350, 0554T, 77085.
What ICD-9 codes does E21.0 map to? +
Per CMS GEMs, E21.0 maps to ICD-9 codes: 25201. Useful for legacy data review and historical claim analysis.
Get the full PayerReady toolkit
Free access to CPT/ICD-10 lookup, denial appeals, fee comparator, and claim auditing with credentialing enrollment.
Start free →Run this code through our claim audit tool
Check NCCI bundling, MUE limits, and modifier logic before submission.
Try the auditor →Did this page help?
Quick signal so we know what to improve.
If you want a code reference page that doesn't exist yet, email coding@payerready.com.
Tell us what's missing or wrong: coding@payerready.com. We respond within 5 business days.
Reviewed by the PayerReady Medical Coding Team
Verified against the CMS 2026 code set on May 31, 2026.
Powered by 11K CPT · 98K ICD-10 · 860K MPFS rates · 4.5M NCCI edits · 9.5M NPIs. Our data methodology · About our coding team