ICD-10 Code I15.2: Hypertension secondary to endocrine disorders

Key Takeaways

ICD-10 Code I15.2 is the billable FY2026 diagnosis code for hypertension secondary to endocrine disorders, effective October 1, 2025.

Sequencing rule: Always code the underlying endocrine disorder (e.g. pheochromocytoma, Cushing’s syndrome, primary hyperaldosteronism) before I15.2, per ICD-10-CM Official Guidelines Section I.C.9.

I15.2 maps to MS-DRG 304 (Hypertension with MCC) or MS-DRG 305 (Hypertension without MCC) under MDC 05 Circulatory System, per CMS MS-DRG v43.0 (FY2026).

Pabau’s structured client records and AI-assisted clinical documentation help practices capture the underlying endocrine etiology needed to support I15.2 at audit.

ICD-10 Code I15.2 is the billable ICD-10-CM diagnosis code for hypertension secondary to endocrine disorders, effective for FY2026. It applies when high blood pressure has a confirmed hormonal cause, such as pheochromocytoma, Cushing’s syndrome, primary hyperaldosteronism, or hyperthyroidism, rather than being idiopathic.

Coders sometimes reach for I15.2 in the wrong situations: Without a documented endocrine cause, when I10 (essential hypertension) actually fits better, or with the sequencing order reversed. This reference covers the code definition, hierarchy, documentation requirements, sequencing rules, MS-DRG mapping, and POA indicator requirements for I15.2.

ICD-10 Code I15.2: Definition and billable status

ICD-10 Code I15.2 is a billable, specific ICD-10-CM code for hypertension secondary to endocrine disorders. The hypertension has a confirmed hormonal cause — the adrenal glands, thyroid, or pituitary drive blood pressure up through a mechanism doctors can identify and, in many cases, treat directly.

Because the cause is endocrine rather than idiopathic, the code falls under category I15 (secondary hypertension) rather than I10 (essential hypertension). The 2026 edition of I15.2 became effective on October 1, 2025, and is valid for FY2026 claims.

Per the CMS ICD-10-CM code files, the code carries the status “Active” and requires no additional digit for specificity at the I15.2 level.

Quick reference: I15.2 code details

The table below summarizes the key code attributes coders need before submitting an I15.2 claim. Cross-check this against the CDC/NCHS ICD-10-CM web tool to confirm effective dates for the current fiscal year.

Clinical overview: What causes hypertension secondary to endocrine disorders?

Endocrine hypertension develops when a hormone-secreting condition drives blood pressure up directly, through excess catecholamines, cortisol, aldosterone, thyroid hormone, or growth hormone. It’s often reversible once the underlying condition is treated, which is why correct identification matters clinically, not just for coding.

Practices using GP clinic software that integrates structured problem lists are better positioned to flag the underlying endocrine condition when the blood pressure presentation first appears. The same applies to metabolic health practices, which manage these hormonal conditions directly and need equally structured documentation to keep coding defensible.

The most common underlying causes are:

• Primary hyperaldosteronism (Conn syndrome): Excess aldosterone from an adrenal adenoma or bilateral adrenal hyperplasia; the most common endocrine cause of secondary hypertension.
• Pheochromocytoma: A catecholamine-secreting adrenal tumor causing sustained or episodic hypertension, often with palpitations, headache, and sweating.
• Cushing’s syndrome: Excess cortisol from an adrenal or pituitary source, or from long-term exogenous steroid use.
• Hyperthyroidism/thyrotoxicosis: Excess thyroid hormone driving systolic hypertension alongside tachycardia.
• Congenital adrenal hyperplasia (CAH): Enzyme deficiencies (e.g. 11-beta-hydroxylase deficiency) that cause excess mineralocorticoid activity.
• Acromegaly: Excess growth hormone causing hypertension alongside its other systemic effects.

A physician diagnosis of endocrine hypertension requires documented confirmation of the underlying hormonal cause, typically via biochemical testing:

• Plasma or urine metanephrines for pheochromocytoma
• Aldosterone-renin ratio for Conn syndrome
• Late-night salivary or serum cortisol for Cushing’s syndrome
• TSH and free T4 for hyperthyroidism

Confirmation often also includes adrenal or pituitary imaging. Without that workup or diagnostic note, the documentation cannot support I15.2 over I10.

I15.2 within the ICD-10-CM hierarchy

Understanding the code hierarchy prevents both undercoding (defaulting to I10 when a specific secondary cause is documented) and overcoding (using I15.2 without a confirmed endocrine etiology). For more on the related parent code, see I10.

Note that I15.0 (renovascular hypertension) and I15.1 (hypertension secondary to other renal disorders) are distinct codes reserved for renal causes. If the documented etiology is a kidney or renal-vascular condition, such as renal artery stenosis, rather than a hormonal one, use I15.0 or I15.1 instead of I15.2.

Approximate synonyms and inclusion terms for I15.2

The ICD-10-CM alphabetical index routes the following clinical terms to I15.2. Coders searching by clinical description rather than code number should confirm the term maps here before assigning the code.

• Secondary hypertension due to pheochromocytoma
• Hypertension due to primary hyperaldosteronism (Conn syndrome)
• Hypertension due to Cushing’s syndrome
• Hypertension due to congenital adrenal hyperplasia
• Hypertension due to hyperthyroidism (thyrotoxicosis)
• Hypertension due to acromegaly

These synonyms reflect how physicians document the diagnosis in clinical notes. When the note uses one of these phrases and confirms the underlying hormonal mechanism, ICD-10 Code I15.2 is the correct assignment.

Excludes notes: What I15.2 does not cover

The Excludes1 and Excludes2 notes apply at the I15 category level, so they cover I15.2 along with the other I15 subcodes. Getting them wrong means missing a required additional code, or incorrectly reporting two codes that must never appear together. For another example of how excludes rules narrow a code’s use, see I99.9.

Key point: Selecting I15.2 over I10 depends entirely on documentation. If the physician’s note only records “hypertension” without confirming and naming the endocrine cause, I10 remains the correct code. I15.2 should never be assigned on the strength of a blood pressure reading alone.

Documentation requirements for coding ICD-10 Code I15.2

Weak documentation is the single most common reason I15.2 claims fail at audit. The physician note must contain specific elements, not just a mention of “hypertension.”

Practices with structured patient records can template these fields into the clinical encounter note, reducing the risk of a missing etiology at submission.

• Confirmed diagnosis statement: The physician must explicitly state “hypertension secondary to [the endocrine condition]” or a mapped synonym. “Elevated blood pressure” or “hypertension, rule out endocrine cause” does not support I15.2.
• Underlying etiology documented: The note must identify the endocrine cause (e.g. “primary hyperaldosteronism confirmed via aldosterone-renin ratio,” “pheochromocytoma confirmed via plasma metanephrines and CT adrenal imaging”).
• Diagnostic workup referenced: Biochemical testing (aldosterone-renin ratio, plasma or urine metanephrines, cortisol testing, TSH/free T4, 17-hydroxyprogesterone for congenital adrenal hyperplasia, IGF-1) or imaging (adrenal CT/MRI, pituitary MRI) supporting the endocrine etiology should appear in or be referenced from the encounter note.
• The specific endocrine disorder coded separately: The underlying condition should carry its own ICD-10-CM code (e.g. E26.01 for primary hyperaldosteronism due to an adrenal adenoma, E24.- for Cushing’s syndrome, E05.- for thyrotoxicosis) alongside I15.2. ICD-10-CM does not split I15.2 by hormone at the code level, so physician documentation carries the specificity.
• Treatment plan relevant to etiology: Note the management plan for the underlying cause (e.g. adrenalectomy, mineralocorticoid receptor antagonist therapy, alpha- and beta-blockade before pheochromocytoma surgery), which confirms clinical specificity.

A coder cannot assume an endocrine cause from a blood pressure reading alone. The documentation must make the link explicit.

ICD-10-CM coding and sequencing guidelines for I15.2

The ICD-10-CM official guidelines (Section I.C.9) establish a clear sequencing hierarchy for secondary hypertension. The underlying endocrine condition codes first. I15.2 follows as an additional diagnosis, which signals to the payer that hypertension is a consequence, not the primary reason for the encounter.

Sequencing order for a patient with primary hyperaldosteronism causing secondary hypertension:

1. Code the underlying endocrine cause first (e.g. E26.01 for primary hyperaldosteronism due to an adrenal adenoma, D35.00 for a benign adrenal tumor such as a pheochromocytoma, E24.9 for Cushing’s syndrome, E05.90 for thyrotoxicosis, E25.0 for congenital adrenal hyperplasia, or E22.0 for acromegaly).
2. Code I15.2 as an additional diagnosis to identify the hypertension as secondary to the endocrine disorder.
3. Add any relevant complication codes if hypertensive end-organ damage is documented (e.g. hypertensive heart disease, CKD stage).

When the principal diagnosis for the inpatient encounter is the underlying endocrine condition (such as a pheochromocytoma requiring adrenalectomy), I15.2 typically appears as a secondary diagnosis. If the encounter is primarily for hypertension management and the endocrine cause is incidental context, the sequencing may differ.

The admitting diagnosis and the reason for the encounter drive the principal diagnosis selection, per the WHO ICD-10 classification guidance and its US ICD-10-CM adaptation.

MS-DRG mapping for ICD-10 Code I15.2

For inpatient claims, I15.2 maps to MDC 05 (Diseases and Disorders of the Circulatory System) under CMS MS-DRG v43.0 (FY2026, effective October 1, 2025).

Hypertension codes split into only two MS-DRGs: The DRG assignment depends on whether a major complication or comorbidity (MCC) is documented in the same encounter, which shifts the reimbursement weight.

Practices using claims management software can reduce DRG assignment errors by validating the MCC capture before claim submission. For another circulatory system code under MDC 05, see I35.1.

Source: CMS MS-DRG v43.0 Definitions Manual, FY2026 (effective October 1, 2025). DRG relative weights are updated annually; confirm the current weight via the AAPC ICD-10-CM code lookup or the CMS IPPS final rule for the applicable fiscal year.

Accurate ICD-10 coding starts with better clinical records

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Present on Admission (POA) indicator for I15.2

The Present on Admission (POA) indicator is required on all inpatient claims submitted to Medicare and Medicaid. It does not apply to outpatient claims. For ICD-10 Code I15.2, the POA indicator is not exempt, meaning the coder must report it based on clinical documentation.

Hypertension secondary to an endocrine disorder is a chronic condition in most patients, so a “Y” indicator is appropriate when the condition was known prior to admission. Always defer to the physician’s documentation rather than inferring POA status from a previous encounter.

How Pabau supports accurate ICD-10 diagnostic coding

Coding accuracy for ICD-10 Code I15.2 depends entirely on the quality of the encounter note. A vague note produces an I10 default. A structured note with the confirmed endocrine etiology, biochemical or imaging results, and treatment plan supports I15.2 without question.

Pabau’s AI-assisted clinical documentation transcribes and structures consult notes in real time, capturing the diagnostic reasoning that coders need to assign specific codes rather than unspecified fallbacks.

Beyond note capture, practices benefit from digital intake forms that collect structured cardiovascular and endocrine history at the point of check-in. This creates an audit trail of the patient’s documented hypertension context before the encounter even begins, and that pre-encounter data, combined with the consultation note, gives coders the full clinical picture.

For practices managing multi-condition chronic patients — such as a patient on insulin pump therapy who also has endocrine hypertension — EHR integration across systems ensures the endocrine diagnosis from a specialist encounter is visible to the primary care coder at follow-up.

Maintaining HIPAA-compliant practice software throughout this documentation chain protects the practice at audit. Practices wanting to reduce documentation overhead for their teams will find practical workflow changes in reduce documentation time.

Conclusion

Miscoding hypertension secondary to endocrine disorders as essential hypertension (I10) is one of the most preventable claim errors in cardiovascular medicine. The confirmed etiology is usually in the record. The documentation just needs to make it explicit enough for the coder to act on.

Pabau’s structured clinical records and client management tools help practices build the documentation habits that support accurate ICD-10 Code I15.2 assignment, reducing denials and strengthening audit readiness. To see how Pabau works for your practice, book a demo with the team.

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