What is the next step for a patient with overt hypothyroidism (Thyroid Stimulating Hormone (TSH) level of 65 and free Thyroxine (T4) level less than 0.3) without symptoms?

Immediate Levothyroxine Initiation for Overt Hypothyroidism

Start levothyroxine immediately regardless of symptoms—a TSH of 65 with free T4 <0.3 represents severe overt hypothyroidism requiring urgent treatment to prevent cardiovascular dysfunction, metabolic complications, and quality of life deterioration. 1

Why Treatment Cannot Wait

The absence of symptoms is irrelevant in overt hypothyroidism. Your laboratory values demonstrate profound thyroid failure that will cause progressive organ damage even without subjective complaints. 1

• Overt hypothyroidism is defined as elevated TSH with low free T4, which you clearly have with TSH 65 and free T4 <0.3. 1
• Treatment prevents cardiovascular dysfunction including delayed cardiac relaxation, abnormal cardiac output, and increased risk of heart failure. 1, 2
• Untreated overt hypothyroidism causes adverse lipid profiles, increasing cardiovascular event risk. 1, 2
• The severity of your thyroid failure (TSH >10 mIU/L) carries approximately 5% annual risk of further deterioration if left untreated. 1

Critical Safety Check Before Starting Treatment

Before initiating levothyroxine, you must rule out concurrent adrenal insufficiency, as starting thyroid hormone before corticosteroids can precipitate life-threatening adrenal crisis. 1, 3

• Check morning cortisol and ACTH levels immediately. 1
• If adrenal insufficiency is present, start physiologic dose steroids 1 week prior to thyroid hormone replacement. 1
• This is particularly important in autoimmune hypothyroidism (check anti-TPO antibodies), as these patients have higher risk of concurrent autoimmune adrenal insufficiency. 1

Levothyroxine Dosing Strategy

Your starting dose depends critically on your age and cardiac status:

For Patients <70 Years Without Cardiac Disease:

• Start with full replacement dose of approximately 1.6 mcg/kg/day. 1, 4
• This rapidly normalizes thyroid function and prevents prolonged metabolic dysfunction. 1

For Patients >70 Years OR With Cardiac Disease:

• Start with 25-50 mcg/day and titrate gradually. 1, 4
• Rapid normalization can unmask or worsen cardiac ischemia in patients with underlying coronary disease. 1
• Increase by 12.5-25 mcg every 6-8 weeks based on TSH response. 1

Monitoring Protocol

Recheck TSH and free T4 in 6-8 weeks after starting treatment. 1, 4

• This represents the time needed to reach steady state with levothyroxine. 1
• Target TSH within reference range of 0.5-4.5 mIU/L with normal free T4. 1
• Continue dose adjustments every 6-8 weeks until TSH normalizes. 1
• Once stable, monitor TSH every 6-12 months or if symptoms change. 1

Administration Instructions

• Take levothyroxine on empty stomach, 30-60 minutes before breakfast. 1
• Separate from iron, calcium supplements, or antacids by at least 4 hours. 1
• Consistency in timing and administration is critical for stable thyroid levels. 1

Common Pitfalls to Avoid

Do not delay treatment waiting for symptoms to develop—overt hypothyroidism causes organ damage regardless of subjective complaints. 1

• Approximately 25% of patients are unintentionally overtreated with TSH fully suppressed, increasing risks for atrial fibrillation, osteoporosis, and cardiac complications. 1
• Avoid adjusting doses more frequently than every 6-8 weeks before reaching steady state. 1
• Never assume hypothyroidism is permanent without reassessment—30-60% of elevated TSH levels may represent transient thyroiditis. 1, 5

Special Considerations

If you are pregnant or planning pregnancy, treatment is even more urgent:

• Untreated maternal hypothyroidism increases risk of preeclampsia, low birth weight, and permanent neurodevelopmental deficits in the child. 1
• Target TSH <2.5 mIU/L in first trimester. 1
• Levothyroxine requirements typically increase 25-50% during pregnancy. 1, 4