A 63-year-old man presents with tiredness and weight gain. Examination shows bradycardia, dry skin and delayed ankle reflexes. TSH is 18 mIU/L (reference 0.4-4.0), free T4 is 8 pmol/L (reference 10-20). He has no significant cardiac disease. According to Australian thyroid management practice, what is the most appropriate initial levothyroxine dose?