What is the appropriate management for an adult patient overtreated with levothyroxine for five months who now has iatrogenic hyperthyroidism, low ferritin, and depressive‑anxiety symptoms?

Management of Iatrogenic Hyperthyroidism with Concurrent Low Ferritin and Psychiatric Symptoms

Immediately reduce the levothyroxine dose by 25–50 mcg to prevent serious cardiovascular and bone complications, while simultaneously addressing the low ferritin and recognizing that the depression and anxiety symptoms are likely direct manifestations of the thyroid overtreatment that should improve with dose correction.

Immediate Thyroid Hormone Dose Reduction

The first priority is to reduce the levothyroxine dose immediately because 5 months of TSH suppression significantly increases risks for atrial fibrillation (3–5 fold), osteoporosis, fractures, and cardiovascular mortality, particularly if the patient is over 60 years old 1.

• Decrease levothyroxine by 25–50 mcg immediately if TSH is suppressed below 0.1 mIU/L 1.
• Decrease by 12.5–25 mcg if TSH is between 0.1–0.45 mIU/L, using the smaller increment if the patient is elderly or has cardiac disease 1.
• Approximately 25% of patients on levothyroxine are unintentionally maintained on doses sufficient to fully suppress TSH, creating serious complication risks 1.

Recheck Thyroid Function Tests

• Measure TSH and free T4 in 6–8 weeks after dose adjustment to evaluate response, targeting TSH within the reference range of 0.5–4.5 mIU/L with normal free T4 1.
• Free T4 helps interpret ongoing abnormal TSH levels during therapy, as TSH may take longer to normalize 1.
• Once adequately treated, repeat testing every 6–12 months or sooner if symptoms change 1.

Understanding the Psychiatric Symptom Connection

The depression and anxiety symptoms are highly likely to be direct consequences of the iatrogenic hyperthyroidism and should improve substantially with thyroid hormone normalization.

• Overt hyperthyroidism frequently causes anxiety, fatigue, poor concentration, and disturbed sleep—all core symptoms of generalized anxiety disorder 2.
• Somatic symptoms such as palpitations, shortness of breath, and increased perspiration overlap with panic disorder manifestations 2.
• Nearly all studies found significant comorbidity between anxiety and thyroid disorders, with an inverse relationship between self-reported anxiety levels and TSH 2.
• Iatrogenic subclinical hyperthyroidism can exacerbate anxiety symptoms and disrupt quality of life, depending on the level of free T4 3.
• The rate of moderate/severe anxiety was significantly higher in patients with exogenous subclinical hyperthyroidism (27.5%) compared to euthyroid controls (9.4%), with TSH levels and anxiety scores significantly negatively correlated 3.

Address Low Ferritin Concurrently

Low ferritin requires evaluation and treatment as it contributes to fatigue and may worsen psychiatric symptoms, but this is a separate issue from the thyroid overtreatment.

• Iron deficiency can cause fatigue, cognitive impairment, and mood disturbances that overlap with thyroid dysfunction symptoms 2.
• Initiate oral iron supplementation (e.g., ferrous sulfate 325 mg daily) if ferritin is low, but take it at least 4 hours apart from levothyroxine to avoid absorption interference 1.
• Recheck ferritin in 8–12 weeks to assess response to supplementation.

Monitoring for Cardiovascular and Bone Complications

Five months of TSH suppression has already created substantial risk for serious complications that require assessment.

• Obtain an ECG to screen for atrial fibrillation, especially if the patient is over 60 years or has cardiac disease, as prolonged TSH suppression significantly increases arrhythmia risk 1.
• Consider bone density assessment (DXA scan) in postmenopausal women or elderly patients, as meta-analyses demonstrate significant bone mineral density loss with TSH suppression 1.
• Patients with chronically suppressed TSH should ensure adequate daily calcium (1200 mg/day) and vitamin D (1000 units/day) intake 1.

Expected Symptom Improvement Timeline

• Psychiatric symptoms should begin improving within 6–8 weeks of normalizing thyroid function, as restoration of euthyroidism is accompanied by improvement in quality of life and psychological symptoms 4.
• Anxiety and depressive symptoms improve more dramatically in overt thyroid dysfunction than in subclinical cases 4.
• If depression and anxiety persist after 3–4 months of euthyroidism, consider primary psychiatric evaluation, but do not initiate psychiatric medications until thyroid function is normalized 2.

Critical Pitfalls to Avoid

• Never ignore suppressed TSH in patients with psychiatric symptoms—the thyroid dysfunction is likely the primary driver and must be corrected first 2, 3.
• Do not assume psychiatric symptoms require antidepressants or anxiolytics before correcting the iatrogenic hyperthyroidism, as these symptoms may resolve completely with thyroid normalization 3, 4.
• Failing to reduce levothyroxine dose when TSH is suppressed perpetuates bone loss and cardiovascular risk, particularly after 5 months of overtreatment 1.
• Adjusting doses too frequently before reaching steady state (should wait 6–8 weeks between adjustments) is a common error 1.

Special Considerations

• If the patient has cardiac disease, atrial fibrillation, or other serious medical conditions, consider repeating testing within 2 weeks rather than waiting the full 6–8 weeks 1.
• For patients over 60 years, the risk of atrial fibrillation is substantially higher with TSH suppression, warranting more aggressive dose reduction 1.
• For postmenopausal women, the risk of bone mineral density loss and fractures is significantly elevated, supporting consideration of bone density assessment 1.