The recommended and appropriate replacement therapy for hypothyroidism is levothyroxine sodium. The initial replacement dose should be low if heart disease is suspected. Because of the long half-life of levothyroxine sodium small dosage adjustments may be performed by adding or withdrawing a tablet once or twice weekly. Levothyroxine sodium is only partly absorbed after oral ingestion, and food, minerals, drugs and tablet composition influence absorption.--Laurberg, P., et al., Hypothyroidism in the Elderly: Pathophysiology, Diagnosis and Treatment. Drugs & Aging, 2005. 22(1): p. 23-38.
Because people with longstanding hypothyroidism may have bradycardia, which can mask substantial but asymptomatic coronary artery disease,31 levothyroxine should be replaced cautiously in older patients (>60 years) or those with known ischaemic heart disease. Particular attention is required in those with profound and longstanding hypothyroidism (thyroid stimulating hormone level >50 mU/l). In these instances, or in someone with active angina pectoris or recent acute coronary syndrome, the starting dose of levothyroxine should be 12.5 or 25 μg daily, which should then be increased every three to six weeks until euthyroidism is achieved.
--Vaidya, B. and S.H.S. Pearce, Management of hypothyroidism in adults. BMJ, 2008. 337
所以，超過六十歲以上的老年人，或是本來就有ischaemic heart disease病史的人，補充thyroxine最好從1/8#或是1/4#(每顆100mcg)補起