E31.21 ICD-10-CM Code: Multiple endocrine neoplasia [MEN] type I
E31.21 maps to CMS-HCC V28 51. A source-labeled RAF reference is available. Confirm the documented diagnosis and applicable coding requirements. MEAT criteria · RAF Calculator · free HCC coding tools
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FY 2026 Apr update / Endocrine, nutritional and metabolic diseases (E00-E89) / Disorders of other endocrine glands (E20-E35)
E31.21
Billable / SpecificICD-10-CMOfficial ICD-10-CMCodebook guidanceMultiple endocrine neoplasia [MEN] type I
A hereditary condition where tumors develop in the pituitary gland, pancreas, and parathyroid glands, causing hormone imbalances.
Buddy Insight
Multiple endocrine neoplasia type I (Wermer syndrome) is an autosomal dominant condition caused by mutations in the MEN1 tumor suppressor gene, predisposing to tumors of the parathyroid glands (95%), pancreatic islet cells (40%), and anterior pituitary (30%).
CMS-HCC V28
MappedHCC 51
Code-level coefficient reference
CMS-HCC V24
HistoricalHistorical
Not used for CY2026 payment
ACA/HHS
MappedHCC 030
Code-level coefficient reference
ESRD/PACE
MappedHCC 23
Code-level coefficient reference
RXHCC
MappedHCC 43
Code-level coefficient reference
Code Book Path
Inclusion Terms
Official- Wermer's syndrome
- Multiple endocrine adenomatosisInherited from E31.2
Excludes 2
OfficialNo Excludes 2 notes are included in this display for E31.21. Check the code and parent instructions in the Code Book.
Related Codes
Includes
OfficialNo Includes notes are included in this display for E31.21. Check the code and parent instructions in the Code Book.
Excludes 1
Official- transitory endocrine and metabolic disorders specific to newborn (P70-P74)Inherited from E00-E89, E20-E35, E31
- galactorrhea (N64.3)Inherited from E00-E89, E20-E35, E31
- gynecomastia (N62)Inherited from E00-E89, E20-E35, E31
- ataxia telangiectasia [Louis-Bar] (G11.3)Inherited from E00-E89, E20-E35, E31
- dystrophia myotonica [Steinert] (G71.11)Inherited from E00-E89, E20-E35, E31
- pseudohypoparathyroidism (E20.1)Inherited from E00-E89, E20-E35, E31
Code First
OfficialNo Code First sequencing instructions are included in this display for E31.21. Check the code and parent instructions in the Code Book.
Use Additional
OfficialNo Use Additional Code instructions are included in this display for E31.21. Check the code and parent instructions in the Code Book.
Code Also
Official- any associated malignancies and other conditions associated with the syndromesInherited from E31.2
Buddy Documentation Tip
MEAT Support
Audit Caution
Common Mistakes
Current with CMS: FY2026 ICD-10-CM Apr 1 update (effective Apr 1 – Sep 30, 2026) · CMS-HCC V28, 100% phased in for payment year 2026. FY2027 code set already staged for October 1, 2026. How HCC Buddy stays current →
Is E31.21 an HCC code?
Yes. E31.21 (Multiple endocrine neoplasia [MEN] type I) maps to HCC 51, Addison's and Cushing's Diseases, Acromegaly, and Other Specified Endocrine Disorders under the CMS-HCC V28 risk adjustment model, with a source-labeled community non-dual aged reference coefficient of 0.510. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes. It is billable for payment year 2026.
Coder answer: E31.21 is billable and maps to V28 HCC 51, Addison's and Cushing's Diseases, Acromegaly, and Other Specified Endocrine Disorders. Open it in the Code Book for the tabular path, RAF, and MEAT checklist.
- Code
- E31.21
- Description
- Multiple endocrine neoplasia [MEN] type I
- HCC (V28)
- HCC 51 — Addison's and Cushing's Diseases, Acromegaly, and Other Specified Endocrine Disorders
- RAF reference coefficient
- 0.510
- Billable
- Yes
- Payment year
- 2026
HCC Category Mapping
These are source-labeled model coefficients, not member totals. A category may still be removed by hierarchy or model cleanup rules. Weights are not directly comparable across models: CMS-HCC V28 and V24 use Community, Non-Dual, Aged; ESRD uses the dialysis continuing-enrollee model; RxHCC is the Part D continuing-enrollee, non-low-income, aged weight (a larger scale than CMS-HCC). ACA/HHS has no single weight — it varies by metal level. Actual per-patient RAF contribution depends on member context, hierarchy and cleanup rules, interactions, and the model year used by the payer. V28 is the CMS-HCC model phased in over payment years 2024–2026; V24 remains available for historical review.
Work E31.21 in the Code Book — tabular path, V28 RAF reference, and MEAT checklist →
MEAT review for E31.21
For E31.21, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule.
- MMonitor: signs, symptoms, disease progression, or lab trending documented in the note
- EEvaluate: test results, medication response, or physical findings reviewed by the provider
- AAssess: explicit mention in the assessment or plan with acknowledgment of status
- TTreat: medication, referral, procedure, therapy, or counseling tied to the diagnosis
Coder workflow notes
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What This Code Means
E31.21 is the ICD-10-CM diagnosis code for multiple endocrine neoplasia [men] type i. A hereditary condition where tumors develop in the pituitary gland, pancreas, and parathyroid glands, causing hormone imbalances. E31.21 sits in the ICD-10-CM chapter for endocrine, nutritional and metabolic diseases (e00-e89), within the section covering disorders of other endocrine glands (e20-e35).
Under the CMS-HCC V28 risk adjustment model, E31.21 maps to Addison's and Cushing's Diseases, Acromegaly, and Other Specified Endocrine Disorders (HCC 51) with a source-labeled community, non-dual, aged reference coefficient of 0.510. No V24 mapping is shown for E31.21; use the applicable model and payment year when reviewing the V28 mapping. For CY2026 non-PACE Medicare Advantage, CMS uses 100% of the 2024 CMS-HCC model (V28). PACE uses a separate model blend. Source-labeled code-level coefficients are references, not member totals. Actual contribution depends on complete member context, hierarchy and cleanup rules, interactions, and model year. HCC Buddy's RAF Calculator supports CMS-HCC V28 PY2026 and shows no score unless every required source and calculation check passes.
Document specific tumors present (pituitary adenoma, gastrinoma, insulinoma, parathyroid adenoma) as secondary diagnoses. For E31.21, confirm that the documentation supports the diagnosis and meets the applicable coding, encounter, program and payer requirements. MEAT (Monitor, Evaluate, Assess, or Treat) is a review mnemonic, not a universal CMS coding rule. When documentation is ambiguous, coders should issue a provider query rather than assume the highest-specificity variant.
HCC Buddy maintains structured V28 and V24 mapping, source-labeled coefficient references, and MEAT documentation criteria for E31.21 sourced directly from the CMS-HCC risk adjustment model files and the CMS ICD-10-CM code set.
Coding Tips
- •Document specific tumors present (pituitary adenoma, gastrinoma, insulinoma, parathyroid adenoma) as secondary diagnoses
- •This is an inherited condition; consider coding family history if relevant to the encounter
Clinical Significance
Multiple endocrine neoplasia type I (Wermer syndrome) is an autosomal dominant condition caused by mutations in the MEN1 tumor suppressor gene, predisposing to tumors of the parathyroid glands (95%), pancreatic islet cells (40%), and anterior pituitary (30%). Primary hyperparathyroidism is usually the earliest manifestation, often presenting before age 30.
Documentation Requirements
- ✓Document MEN1 genetic testing results, which endocrine tumors are present (parathyroid adenoma, gastrinoma, insulinoma, prolactinoma), tumor sizes and locations on imaging, hormone levels for each affected gland, surgical history, and surveillance protocol for tumor screening.