A 52-year-old woman from rural Maharashtra presents with a 6-month history of progressive fatigue, weight gain of 8 kg despite poor appetite, and constipation. She reports feeling cold even in warm weather and notices her skin has become dry and rough. On examination, her heart rate is 48 bpm, blood pressure is 138/88 mmHg, and there is a non-tender diffuse thyroid enlargement. Reflexes show delayed relaxation phase. Laboratory investigations reveal TSH 18.5 mIU/L (normal 0.4–4.0), free T4 0.8 ng/dL (normal 0.8–1.8), and serum cholesterol 285 mg/dL. Anti-TPO antibodies are positive at 320 IU/mL. What is the most appropriate initial management?

Explanation

## Clinical Diagnosis **Key Point:** This patient has overt primary hypothyroidism (elevated TSH, low-normal free T4, positive anti-TPO antibodies) consistent with Hashimoto's thyroiditis, the most common cause of hypothyroidism in iodine-sufficient regions. ## Rationale for Levothyroxine Dosing Strategy **High-Yield:** In overt hypothyroidism, especially in older patients or those with cardiac comorbidities, levothyroxine must be started at a LOW dose and titrated GRADUALLY to avoid precipitating angina, arrhythmias, or acute decompensation. **Clinical Pearl:** This patient is 52 years old with borderline hypertension (138/88 mmHg) and bradycardia (48 bpm). Starting at 25 mcg and increasing by 25 mcg every 6–8 weeks minimizes the risk of cardiac stress while allowing TSH to normalize progressively. ## Dosing Strategy | Parameter | Rationale | |-----------|----------| | **Initial dose: 25 mcg** | Low starting dose in older/cardiac-risk patients | | **Titration interval: 6–8 weeks** | Allows steady-state achievement and TSH re-equilibration | | **Increment: 25 mcg per step** | Gradual, safe escalation | | **Target TSH: 0.5–2.0 mIU/L** | Goal for symptom relief and cardiovascular safety | ## Key Management Principles 1. **Absorption optimization:** Levothyroxine should be taken on an empty stomach, 30–60 minutes before breakfast, away from calcium, iron, and PPIs. 2. **Monitoring:** TSH should be rechecked 6–8 weeks after each dose adjustment; free T4 can be used to confirm adequate replacement. 3. **Symptom resolution:** Fatigue and cold intolerance typically improve within 2–4 weeks; weight loss and cholesterol normalization take 8–12 weeks. **Mnemonic:** START LOW, GO SLOW — **S**tart at 25 mcg, **T**itrate by 25 mcg, **A**djust every 6–8 weeks, **R**echeck TSH, **T** target TSH 0.5–2.0; **G**radual dose escalation, **O**ld age/cardiac disease = slower titration, **S**teady-state in 6–8 weeks, **L**evothyroxine monotherapy, **O**n empty stomach, **W**atch for over-replacement. [cite:Harrison 21e Ch 405]