1. Replacement therapy with thyroxine is used, which is converted in the periphery to T3. The dose is usually 1.8 ug/kg with a little higher in children and pregnancy (2 ug/kg especially for 4–6 weeks) and lower in elderly (0.5 ug/kg). Keep TSH >0.5 mu/L. 2. In younger patients and those without coronary artery disease, the replacement dose may be started, but in elderly and patients with heart disease, it is necessary to gradually increase the dose every 2–4 weeks according to the TSH levels, as necessary. In pregnancy, one should measure the TSH almost every month. 3. In pregnancy, the dose requirement is increased, and it starts after the 1st month and plateaus at 4–5 months. 4. In congenital hypothyroidism, the hormone levels and therapy should be started within the first 2 weeks of life to avoid mental retardation and the consequences of hypothyroidism. 5. In SCH, treatment with thyroxine depends on the symptoms and presence of antibodies. Most physicians would start treatment. 6. Patients with thyroid cancer after thyroidectomy need thyroxine not only for hypothyroidism but to prevent the cancer also. 7. In myxedema coma, treatment should not be delayed and started with thyroxine (combination of T4 and T3 formulations) or T4 200–400 mcg IV stat and then 50–100 mcg daily till patient can take orally. Lower doses are used in elderly and heart disease patients. T3 is give as 5–15 ug stat and about 2.5–10 ug IV eight hourly till the patient is clinically stable. Add hydrocortisone 100 mg IV eight hourly (till hypoadrenalism is excluded). Fluids, glucose, electrolytes, hypotension, hyponatremia, hypothermia, and so on must be managed. Mechanical ventilation may be required. 8. Patients are advised to take thyroxine while fasting for at least four hours and avoid food and other drugs for at least 20–30 minutes. It is important that the bioavailability of the drug varies with different brands and country. 9. If the patient cannot take orally (postoperative), then thyroxine may be given at 70–80 percent of the dose IV daily. 10. For poorly compliant patients, it may be necessary to give the total weekly dose once per week (do not use in patients with heart disease). 11. Some patients (less than 10 percent) may normalize their thyroid function after thyroxine replacement and may not require further therapy. |