Secondary Hypothyroidism ICD-10-CM Codes

Discover the specific ICD-10 codes for diagnosing and treating secondary hypothyroidism that follow coding guidelines for accurate medical billing.

By Wynona Jugueta on Aug 8, 2025.

Fact Checked by Gale Alagos.

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What are secondary hypothyroidism ICD-10 codes?

Secondary hypothyroidism is a form of thyroid dysfunction caused by a failure of the pituitary gland to produce enough thyroid-stimulating hormone (TSH), which disrupts the normal function of the thyroid gland. This hormonal imbalance reduces thyroid hormone production, contributing to various symptoms and systemic effects. Accurate ICD-10-CM coding is essential for proper documentation and billing, especially in metabolic diseases or pituitary hormone deficiencies. Below are the most frequently used and billable ICD-10 codes for secondary hypothyroidism, updated for 2025:

E03.8 – Other specified hypothyroidism: This is a primary ICD-10-CM code used for secondary hypothyroidism when clearly documented. It includes atypical or complex presentations such as autoimmune hypothyroidism or hypothyroidism associated with thyroid nodules or damage to thyroid tissue not covered by other codes.
E03.2 – Hypothyroidism due to medicaments and other exogenous substances: Used when secondary hypothyroidism arises from drug induced hypothyroidism, such as adverse effects from medications that impair pituitary function or thyroid hormone synthesis.
E03.9 – Hypothyroidism, unspecified: This broad code includes cases where the type of hypothyroidism is not clearly identified in records. It may apply to subclinical hypothyroidism or early stages of hormone deficiency when clinical details are limited.
E89.0 – Postprocedural hypothyroidism: Assigned when hypothyroidism results from surgery, such as pituitary or thyroid cancer removal, or after radiation therapy affecting the endocrine axis.

Other hypothyroidism issues are also tackled by these codes:

E02 – Subclinical iodine-deficiency hypothyroidism: Though rarely used for secondary cases, this may apply when subclinical hypothyroidism due to iodine deficiency is an early finding.
E01.2 – Iodine-deficiency-related multinodular (endemic) goiter: This code is applicable in complex cases where an enlarged thyroid gland due to iodine deficiency leads to hypothyroid symptoms or contributes to congenital central hypothyroidism.

Which secondary hypothyroidism ICD-10 codes are billable?

E03.8: Yes
E03.2: Yes
E03.9: Yes
E89.0: Yes
E02: Yes
E01.2: Yes

All six codes are valid and billable as of the 2025 ICD-10-CM updates. However, E03.8 remains the most clinically relevant for true secondary hypothyroidism cases. To code secondary hypothyroidism accurately, you must identify and code the underlying cause of the pituitary or hypothalamic dysfunction first.

Clinical information

Secondary hypothyroidism is a nuanced endocrine disorder most commonly caused by impaired pituitary gland function. Here's what healthcare professionals need to know:

The condition results from insufficient TSH production, leading to inadequate stimulation of the thyroid gland and reduced secretion of thyroid hormones. This causes primary hypothyroidism-like symptoms even though the root issue lies upstream.
It is often linked to pituitary hormone deficiencies, congenital hypothyroidism, post-surgical damage, or drug-induced hypothyroidism. Patients may also present with complications from thyroid cancer treatment or the removal of thyroid tissue.
Clinical symptoms may include persistent fatigue, cold intolerance, depression, weight gain, slowed cognition, and menstrual irregularities, many overlapping with other metabolic diseases.
Laboratory findings typically show low TSH and low free T4, distinguishing it from primary hypothyroidism (which features high TSH). Imaging and pituitary function testing may be required to confirm the diagnosis.
Treatment includes thyroid hormone replacement (e.g., levothyroxine) tailored to the patient’s needs. If an enlarged thyroid gland, thyroid nodules, or thyroid cancer are present, additional therapies or surgical evaluation may be necessary.

Understanding and documenting the nuances of secondary hypothyroidism ensures precise diagnosis, supports proper billing, and guides individualized care for patients with complex thyroid dysfunction profiles.

Synonyms include:

Pituitary hypothyroidism
Central hypothyroidism
Tertiary hypothyroidism
Hypothyroidism due to pituitary disease
Hypothyroidism due to hypothalamic disorder

Commonly asked questions

Use a secondary hypothyroidism ICD-10 code when a confirmed diagnosis is made based on clinical evaluation and laboratory findings showing central (not primary) origin. Document the underlying cause, such as a tumor, surgical history, or medication-induced suppression.

Treatments include thyroid hormone replacement, primarily levothyroxine, and addressing the root cause, such as surgical intervention for pituitary tumors or stopping causative medications. Long-term endocrine follow-up is recommended.

This code indicates a form of hypothyroidism stemming from inadequate TSH production due to pituitary or hypothalamic dysfunction. It informs both clinical management and insurance billing by identifying the condition’s central origin.

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