Study of the pituitary-thyroid axis in euthyroid goiter after partial thyroidectomy.

The aim of this study was to investigate the time involved after hemithyroidectomy in reaching a new steady state in thyroid function and the relationship between thyroid hormones, basal TSH levels and TSH response to TRH. The investigations were performed on 35 patients 12-18 months after partial thyroidectomy in the first investigation and after 24-30 months in the second investigation. Tests included T4, T3, FT4, FT3 serum levels, basal serum TSH and TSH response to TRH. None of the patients received thyroid replacement and 38 healthy subjects of comparable age and sex were used as controls. We conclude that: i) the time involved in reaching a new steady state of thyroid function in hemithyroidectomized patients is variable and may take a long time; ii) TSH response to TRH returns to the normal range later than thyroid hormone and basal TSH levels.