[Determination of the optimal L-thyroxine dosage for treating nontoxic goiter].

303 patients with non-toxic goitre (aged 14-85 years) were studied to determine the extent to which the level of thyroid-hormone dosage until a negative TRH test is reached can be defined in terms of age, body surface area and goitre size. In all instances detailed examination had determined regular hormone intake. The required L-thyroxine dose (until negative TRH test) was 100 micrograms/d in 75.6% of cases, 125 micrograms/d in 9.2% and 150 micrograms/d in 8.6% of cases. In 2.6% of cases was a satisfactory suppression reached at 50 microgram/d and in 4% at 75 micrograms/d. There was no correlation of the level of L-thyroxine dose to body surface area, age, T3 level, delta-TSH or goitre size. There was a slight correlation between T4 level and optimal L-thyroxine dose, but not significant because of the wide range of normal. The results indicate that the only way to obtain optimal L-thyroxine dosage in the treatment of goitre is by doing a TRH test in the given patient.