Effect of Selective Goitre Resection on Absent Thyrotrophin Response to Thyrotrophin Releasing Hormone in Idiopathic Euthyroid Goitres

Abstract

Absent thyrotrophin (TSH) response to thyrotrophin releasing hormone (TRH) was found in ten of fifty consecutive nodular goitrous patients who were clinically and biochemically euthyroid. These ten patients together with a reference group engaging fifty-eight healthy individuals matched for sex, age, and geographic region form the basis of the present study. Patients with autonomously functioning single adenomata were excluded from the investigation. In the patient group, values of serum thyroxine (T4), free T4-index, and serum TSH did not differ significantly from those recorded in the reference group, whereas serum triiodothyronine was found to be significantly higher in the patients, although within the normal range. After selective resection of the goitre, the TSH responsiveness to TRH recovered completely. Routine indices of thyroid function, however, demonstrated no major deviation from pre-operative levels. During a follow-up period of 1 year, no systematic alterations were recorded in TSH response to TRH nor in the thyroid function tests, indicating maintenance of euthyroidism with restored normality within the pituitary-thyroid axis. The present study lends support to the view that increasing functional autonomy apparently is a common trend in goitre evolution in a non-endemic area.

Preclinical hyperthyroidism - a graded condition

“…Following surgical resection of autonomously secreting goitrous tissue and after recovery of adequate thyrotrophin secretion no change of the circulating thyroid hormone concentrations (Blichert-Toft et al 1978) or only a small decrease in the mean FT4-I ) were observed. In several patients the pre-operative thyroidal function may therefore reflect an actually normal or even low normal autonomous thyroid hormone secretion (during transient TSH defi¬ ciency), which may not exceed the thyroid hor¬ mone supply under normal (recovered) endo¬ genous TSH stimulation.…”

Thyroid function after resection for non-toxic goitre with special reference to thyroid lymphocytic aggregation and circulating thyroid autoantibodies

“…The transient rise discovered may simply be ex¬ plained by the fact that the high normal pre¬ operative level of serum TT3 normalized after operation. It is well established that nodular goitres are able to develop varying degrees of functional autonomy resulting in preclinical hyperthyroidism with raised serum TT3 (Gemsenjäger et al 1976;Blichert-Toft et al 1978). Actually, some of our patients probably had borderline T3-thyrotoxicosis.…”

“…After selective resection of the nodular goitre the function of the pituitary-thyroid axis has been shown to be restored with normalization of serum TT3 (Blichert-Toft et al 1978). This observation may explain the hormonal changes in our study.…”

“…Recent studies, however, have questioned the rational basis for routine in¬ take of thyroid hormone after simple goitre resec¬ tion in non-endemic areas (Blichert-Toft et al 1978, 1979Matte et al 1981;Geerdsen & Hee 1982;Persson et al 1982). In these studies, im¬ paired thyroid function after resection was a rare finding, and thyroid replacement therapy does not seem to be efficacious in preventing regrowth of goitre (Persson et al 1982;Gemsenjäger et al 1983).…”

Invited commentary

“…As noted, the "lesion" in nontoxic nodular goiter may be diffuse. However, there are also a number of reports indicating that following the removal of a hyperfunctioning area of a nontoxic nodular goiter the previous abnormal TSH response (flat TRH-TSH) returns to normal, indicating the reestablishment of a normal TRH-TSH feedback mechanism [2]. The authors argue that with a relative autonomy of function, the only indication for thyroid hormone administration in the postoperative period is hypothyroidism.…”