[Effect of a 2 mg thyroxine bolus on the hypophyseal-thyroid axis (author's transl)].

The effect of a single dose of 2 mg L-thyroxine on central and peripheral parameters of the hypophyseal-thyroid axis was studied on ten euthyroid and ten hypothyroid patients, and ten with euthyroid goitre. Without the occurrence of hyperthyroid symptoms, the T4 serum level was raised for five days in the euthyroid group, for 11 days in the hypothyroid ones. During this time the T3 serum level did not alter. Suppression of iodine uptake by the thyroid and TSH secretion of the hypophysis persisted longer, both for basal and TRH-stimulated liberation, than the substitution effect. Even when the T4 bolus has to be at a higher total T4 dose for the same therapeutic effect than with daily small single doses, it is a comparable alternative to present-day forms of treatment. It is of particular advantage where there are medical reasons for widely spaced drug intake or rapid normalisation of the T4 serum level is deemed desirable.