What is the ICD‑10‑CM code for overt (clinical) hypothyroidism?

ICD-10-CM Code for Overt Hypothyroidism

The ICD-10-CM code for overt (clinical) hypothyroidism is E03.9 (Hypothyroidism, unspecified) when the specific etiology is unknown, or more specific codes such as E03.8 (Other specified hypothyroidism) or E06.3 (Autoimmune thyroiditis/Hashimoto's) when the underlying cause is documented.

Understanding Overt vs. Subclinical Hypothyroidism

Overt hypothyroidism is defined by elevated TSH with low free T4, distinguishing it from subclinical hypothyroidism where free T4 remains normal 1, 2. This biochemical distinction is critical for proper coding and clinical management 3.

• Overt hypothyroidism presents with TSH >4.5 mIU/L and free T4 below the reference range 1, 3
• The condition affects 0.3-12% of the population worldwide, with higher prevalence in women and older adults 2
• Untreated overt hypothyroidism can progress to myxedema coma with mortality rates up to 30% 2

Primary ICD-10-CM Codes for Hypothyroidism

Most Common Codes

• E03.9 – Hypothyroidism, unspecified: Use when the specific cause is not documented 1
• E06.3 – Autoimmune thyroiditis: Use for Hashimoto's thyroiditis, which accounts for up to 85% of hypothyroidism cases in iodine-sufficient areas 2, 4
• E03.8 – Other specified hypothyroidism: Use when a specific non-autoimmune cause is documented 1

Additional Specific Codes

• E89.0 – Postprocedural hypothyroidism: For hypothyroidism following thyroidectomy or radioiodine treatment 5
• E03.0 – Congenital hypothyroidism with diffuse goiter: For congenital cases 1
• E03.1 – Congenital hypothyroidism without goiter: For congenital cases without goiter 1

Clinical Documentation Requirements

To code accurately, documentation must specify:

• TSH level (elevated) and free T4 level (low) confirming overt disease 1, 3
• Underlying etiology when known (autoimmune, post-surgical, drug-induced, etc.) 2, 4
• Whether the patient is treatment-naive or on levothyroxine replacement 1

Common Clinical Presentations Requiring This Code

Patients with overt hypothyroidism typically present with:

• Fatigue (68-83% of cases), weight gain (24-59%), and cognitive impairment (45-48%) 2
• Menstrual irregularities (approximately 23%), including oligomenorrhea and menorrhagia 2
• Cardiovascular manifestations including hypertension, dyslipidemia, and increased heart failure risk 4, 5
• Nonspecific symptoms that may be subtle, especially in older adults 4

Important Coding Considerations

Do not confuse with subclinical hypothyroidism codes, which would apply when TSH is elevated but free T4 remains within normal range 1, 3. Subclinical hypothyroidism has different treatment thresholds and prognostic implications 1.

• Approximately 3-13.6% of women and 0.7-5.7% of men have subclinical hypothyroidism, which may progress to overt disease 5
• The annual progression rate from subclinical to overt hypothyroidism is approximately 5% when TSH exceeds 10 mIU/L 1

Documentation Pitfalls to Avoid

• Coding based on symptoms alone without biochemical confirmation (TSH and free T4 levels must be documented) 3
• Failing to specify the underlying cause when known (e.g., using E03.9 when Hashimoto's is documented) 2
• Confusing treated hypothyroidism (patient on stable levothyroxine with normal TSH) with active overt disease 1