Function of pituitary-thyroid axis after surgical treatment of non-toxic nodular goitre

Endemic goiter and endemic thyroid disorders

The primary role of iodine deficiency in goitrogenesis and the prevention and treatment of endemic goiter by iodine supplementation is firmly established. Unfortunately, implementation of iodine prophylaxis programs has met with considerable technical and socioeconomic difficulties. Besides, lack of knowledge concerning some of the other causative factors of endemic goiter has prevented development of appropriate measures for its complete eradication in those areas where goiter persists in spite of prolonged and adequate iodine supplementation. At present, no less than 5% of the world's population have goiters and associated disorders, resulting in a public health and socioeconomic problem of major proportions. Seventy-five percent of people with goiter live in less developed countries where iodine deficiency is prevalent. Goiter prevalence rates of more than 50% and the highest frequency of severe cases of iodine deficiency disorders, namely, cretinism, congenital hypothyroidism, and various degrees of impairment of growth and mental development are found in endemic areas with extreme iodine deficiency. Goiters are usually multinodular and of very large size, producing, on occasion, signs of compression that require surgery. Recurrence rates are as high as 25-30% and second surgery accounts for 16% of all thyroidectomies. Unfortunately, most of these goiters occur in areas with highly restricted medical and surgical facilities. Twenty-five percent of people with goiters live in more developed countries where goiter continues to occur in certain areas despite iodine prophylaxis. Iodine-sufficient goiters are associated with autoimmune thyroiditis, hypothyroidism, hyperthyroidism, and thyroid carcinoma. Goiter is of considerable surgical significance in iodine-sufficient endemic areas and, to a lesser degree, in nonendemic areas where it is called "sporadic" goiter. Recurrence rates of iodine-sufficient goiter are 10-19% following thyroidectomy. Since most of these goiters grow by mechanisms other than increased thyrotropin (TSH) stimulation, treatment with suppressive doses of L-thyroxine is inefficient and, because of possible complications, not recommended. Although Graves' hyperthyroidism is not directly related to endemic goiter, it does relate adversely with ingestion or administration of iodine. At present, Graves' disease is treated with 131I or antithyroid drugs in more than 90% of the cases. The incidence rates of papillary, follicular, and anaplastic thyroid carcinomas appear to be related to endemic goiter and iodine supplementation, with surgery being required in essentially all of these cases.

Thyroid function after surgery for autonomous and non-autonomous nodular endemic goitre--effect of iodide-substitution

The aim of this study was to evaluate the influence of postoperative iodide-substitution on the function of thyroid remnants of different quality and quantity in order to define the appropriate prophylaxis (iodide or thyroid hormone) to prevent recurrent goitre. In a prospective, randomized clinical trial, the following patients were examined: group I: simple, non-autonomous nodular goitre, bilateral thyroidectomy (n = 40); group II: simple, non-autonomous nodular goitre, "selective" (unilateral) thyroidectomy (n = 40); group III: autonomous nodular goitre, bilateral thyroidectomy (n = 40); group IV: autonomous nodular goitre, "selective" (unilateral) thyroidectomy (n = 35). The following parameters were measured 6 and 12 weeks postoperatively. Serum-total-T4, -T3, -TSH, TRH-test, 99mTc-Thyroid-Uptake (TcTU). Six weeks postoperatively the 4 groups were separately randomized into controls and treatment groups, who received 200 micrograms iodide/day orally. Six weeks postoperatively, patients in group I had lower T4 levels and both basal and stimulated TSH were higher than in the other groups, however no significant differences were observed in T3, T4/T3 ratio and TcTU. Twelve weeks postoperatively patients from groups I, II and III, who had been treated with iodide, had lower T3 and TcTU values but higher T4 and T4/T3 than the appropriate controls. Basal and stimulated TSH showed no differences between controls and iodide-treated patients in these groups. In group IV, T4 and T3 showed a tendency to elevation (n.s.), and basal and stimulated TSH as well as TcTU were lower in patients with iodide.(ABSTRACT TRUNCATED AT 250 WORDS)

Recurrence of nontoxic goitre with and without postoperative thyroxine medication

The incidence of postoperative recurrence of nontoxic goitre was evaluated in 175 patients. The average observation period was 8.8 years. Levothyroxine (Eltroxin) had been taken by 104 of these patients as long-term prophylaxis against goitre recurrence. Ten (9.5%) of the 104 had recurrence. The other 71 patients received no or only brief thyroxine medication postoperatively. In this group there were eight recurrences (11.3%). The difference was not significant, nor did the two groups differ significantly in regard to sex and age distribution, pathologic anatomy and observation time. Routine long-term administration of thyroxine after thyroid resection is not justified from the results of this study.

Propranolol improves the impaired TSH response to TRH in patients with autonomously functioning euthyroid multinodular goitre

Ten patients with autonomously functioning euthyroid multinodular goitre received propranolol (Inderal Retard 160 mg daily) for 4 weeks in order to investigate whether normalization of the TRH test or an increased TSH response to TRH could be obtained by decreasing serum T3 levels. Serum T3 decreased significantly after 2 and 4 weeks of propranolol administration. Serum T4 increased during this period, although the change was only significant after 4 weeks of propranolol. T3 resin uptake did not change. The TSH response to TRH increased significantly during the administration of propranolol. Mean delta TSH basally was 1.0, range 0-3.9 mU/l, and mean delta TSH after 4 weeks of propranolol was 2.4, range 0-9.3 mU/l. A strong correlation was found between the increase in delta TSH and the decrease in serum T3 after 4 weeks of propranolol. After withdrawal, delta TSH and T3 returned to premedication levels. Our data suggest that T3 is an important factor in the impairment of the TSH response to TRH in our patients. Normalization of the TRH test was, however, not obtained. These findings support the concept of subclinical hyperthyroidism in 'euthyroid' multinodular goitre with autonomous function.