2027 ICD-10-CM Diagnosis Code E26.01Conn's syndrome

ICD-10-CM Codes›E00–E89›E20-E35›E26

ICD-10-CM E26.01
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

E26.01 is a billable ICD-10-CM diagnosis code for Conn's syndrome. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 643 through 645. Coders also document this condition as adrenal adenoma. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Other specified and unspecified endocrine disorders.

E26.01 no longer risk-adjusts for Medicare Advantage: it mapped to HCC 23 under the retired CMS-HCC V24 model through payment year 2025 but maps to no category in the live V28 model. It still risk-adjusts in the PACE (CMS-HCC V22) category 23, ESRD (V21) category 23, ESRD (V24) category 23, and RxHCC Part D (V08) category 43 for payment year 2027.

Code Identity

ICD-10-CM Code
E26.01
Billable Status
Yes — Valid for Submission
Code Describes
Conn's syndrome
Short Description
Conn's syndrome
Same as the full description in the CMS dataset.
Parent Code
E26.0
Primary hyperaldosteronism

Code Classification

ChapterE00–E89Endocrine, nutritional and metabolic diseases
SectionE20-E35Disorders of other endocrine glands
CategoryE26Hyperaldosteronism
This CodeE26.01Conn's syndrome

Medicare Risk Adjustment (HCC)Billing

E26.01 no longer risk-adjusts for Medicare Advantage: it maps to no payment category in the live CMS-HCC V28 model, although it still risk-adjusts in the other CMS models shown below.

CMS-HCC V28 (Medicare Advantage Payment Model)
Not mapped
Dropped in V28 see all codes that no longer risk-adjust
Prior Model (CMS-HCC V24)
HCC 23
V24 retired last contributed to a Medicare Advantage risk score in payment year 2025
Other CMS Models
PACE (CMS-HCC V22): HCC 23 · ESRD (V21): HCC 23 · ESRD (V24): HCC 23
ESRD V21 weights: 0.013 dialysis, 0.234–0.359 functioning graft · ESRD V24 weights: 0.036 dialysis, 0.217–0.390 functioning graft
Part D (RxHCC)
RxHCC 43 — Pituitary, Adrenal Gland, and Other Endocrine and Metabolic Disorders
also risk-adjusts in the Part D prescription drug model (V08)

Source: CMS Payment Year 2027 risk adjustment mappings and model software. Weights are relative factors, not dollar amounts; a beneficiary's total RAF also includes demographics and interactions. Browse all CMS-HCC categories.

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Adrenal adenoma
  • Adrenal cortical adenoma
  • Aldosterone-producing adenoma
  • Benign neoplasm of adrenal cortex
  • Hyperaldosteronism due to neoplasm of the adrenal cortex
  • Primary hyperaldosteronism due to adrenal adenoma

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to E26.01: its own notes plus those printed at block E20-E35 and Chapter 4. A note printed at a category, block or chapter applies to every code under it.

Excludes1

Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.

From Block E20-E35 Disorders of other endocrine glands applies to 99 codes
From Chapter 4 (E00-E89) Endocrine, nutritional and metabolic diseases applies to 973 codes
  • transitory endocrine and metabolic disorders specific to newborn (P70-P74)

Code Also

A second code may be needed to fully describe the condition; the note gives no sequencing direction.

Notes

General instructions on how these codes are used.

From Chapter 4 (E00-E89) Endocrine, nutritional and metabolic diseases applies to 973 codes
  • All neoplasms, whether functionally active or not, are classified in Chapter 2. Appropriate codes in this chapter (i.e. E05.8, E07.0, E16-E31, E34.-) may be used as additional codes to indicate either functional activity by neoplasms and ectopic endocrine tissue or hyperfunction and hypofunction of endocrine glands associated with neoplasms and other conditions classified elsewhere.

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name E26.01, its category, or a range that includes it.

Code First 1

These codes say to code first a condition named in the note, and E26.01 is one of the conditions named.

  • G63 Polyneuropathy in diseases classified elsewhere
    endocrine disease, except diabetes (E00-E07, E15-E16, E20-E34) names E20-E34, which includes this code

Notes 1

These notes mention E26.01.

  • Chapter 4 (E00-E89) Endocrine, nutritional and metabolic diseases
    All neoplasms, whether functionally active or not, are classified in Chapter 2. Appropriate codes in this chapter (i.e. E05.8, E07.0, E16-E31, E34.-) may be used as additional codes to indicate either functional activity by neoplasms and ectopic endocrine tissue or hyperfunction and hypofunction of endocrine glands associated with neoplasms and other conditions classified elsewhere. names E16-E31, which includes this code

Index to Diseases and InjuriesGuidance

Alphabetical index entries that point to this code.

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

  • Conn Syndrome

    primary hyperaldosteronism caused by the excess production of aldosterone by an adenoma of the zona glomerulosa or conn adenoma.

Patient EducationClinical

Adrenal Gland Disorders

Your adrenal glands are two small organs that sit on top of each kidney. The adrenal glands make different types of hormones you need to stay alive and healthy. Hormones are chemicals that travel in your bloodstream and control how different parts of your body work.

The full article covers:

  • What are adrenal glands?
  • What are adrenal gland disorders?
  • What causes adrenal gland disorders?
  • How are adrenal gland disorders diagnosed?
  • What are the treatments for adrenal gland disorders?

Read the full article at MedlinePlus

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

Convert E26.01 to ICD-9-CMHistory

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

ICD-9-CM
255.12 Conn's syndrome
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 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About E26.01Overview

What is the ICD-10 code for Conn's syndrome?

The ICD-10-CM code for Conn's syndrome is E26.01 (sometimes written as E2601). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is E26.01 (Primary hyperaldosteronism) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report Conn's syndrome on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What MS-DRG does E26.01 group to?

When Conn's syndrome is the principal diagnosis on an inpatient stay, it groups to MS-DRG 644, 645, 643, with relative weights from 0.7461 to 1.6138 depending on complications. Higher weights mean higher Medicare reimbursement.

Can E26.01 be reported with N64.3?

Not as a rule. The Excludes1 note at block E20-E35, which applies to E26.01, lists "galactorrhea (N64.3)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).

What is the ICD-9 equivalent of E26.01?

Under the General Equivalence Mappings, Conn's syndrome converts to ICD-9-CM 255.12 (Conn's syndrome). The mapping is a direct match.

Does E26.01 risk-adjust for Medicare Advantage payment?

Not for Medicare Advantage. E26.01 mapped to HCC 23 in the retired CMS-HCC V24 model, which last determined payment in 2025, but it maps to no category in the live V28 model; see all codes that no longer risk-adjust. It still risk-adjusts in the PACE (CMS-HCC V22) category 23 (Other Significant Endocrine and Metabolic Disorders), ESRD (V21) category 23 (Other Significant Endocrine and Metabolic Disorders), ESRD (V24) category 23 (Other Significant Endocrine and Metabolic Disorders), and RxHCC Part D (V08) category 43 (Pituitary, Adrenal Gland, and Other Endocrine and Metabolic Disorders).