A Report of the Mayo Clinic Experience on the Levothyroxine Absorption Test

BackgroundThe optimal starting replacement dose of levothyroxine (L-T 4 ) related to body weight (BW) is about 1.6 to 1.8 μg/kg/day in hypothyroid adults (1).This dosage can vary according to the etiology and severity of the hypothyroidism, the patient's age, and any associated comorbidities (1).Consequently, the dose of L-T 4 should be adjusted on the basis of the evaluation of serum thyrotropin (TSH) levels, which represent the best marker of the adequacy of L-T 4 prescription in primary hypothyroidism; the TSH cut-off level should be targeted according to the patient's age and other factors, as mentioned above (1,2).