Ongoing management of thyroxine replacement therapy for hypothyroidism in adults

Once levothyroxine therapy is stabilised, measure serum TSH concentration (or in the case of hypopituitarism, serum T₄ concentration) at about 3 and 6 months, and annually thereafter. Most cases of hypothyroidism are lifelong and require indefinite thyroxine replacement.

Transient deficiency can occur following subacute thyroiditis, radioiodine therapy, subtotal thyroidectomy, pregnancy, or treatment with some drugs (see also Drugs that influence thyroid hormones). In these patients, consider trialling a withdrawal of levothyroxine (for 4 to 6 weeks) after around a year of treatment to determine whether long-term treatment is necessary. This could also be considered in a patient who is stable on a low dose of levothyroxine (eg 25 to 50 micrograms). If the serum TSH and serum T₄ concentrations are normal without levothyroxine, therapy does not need to be restarted. If the serum TSH concentration increases (primary hypothyroidism) or if the serum T₄ concentration falls below the reference range without an elevated TSH (central hypothyroidism), restart treatment at the previous dose.