Autonomously functioning thyroid nodules (Plummer disease)

Repetitive monomorphic ventricular tachycardia in a 4-year-old boy with toxic multinodular goiter

A case of toxic multinodular goiter associated with repetitive monomorphic ventricular tachycardia (VT) is reported. A 4-year-old boy was found to have asymptomatic VT. When treatment with antiarrhythmic agents turned out to be ineffective, thyrotoxicosis was suspected due to the rapid enlargement of the left thyroid gland and associated thyroid function studies. A diagnosis of toxic multinodular goiter was made on the basis of subsequent scintigraphy and ultrasonography. Treatment with antithyroid drugs and inorganic iodine restored the thyroid function to normal, and was accompanied by the disappearance of VT. A left thyroid lobectomy was performed, and the pathological findings were compatible with toxic multinodular goiter. After the operation, the patient was transiently hypothyroid and had no VT without medication. A review of the literature revealed no previously documented cases of VT with toxic multinodular goiter.

Toxic nodular goitre

Toxic nodular goitre is the late result of a slow growth process generating new daughter follicles from the mother follicles of a normal thyroid gland. Since the normal follicular shell is not built up by monoclonal epithelial cells, but rather by cells with widely variable functional equipment, daughter follicles generated by the preferential replication of particular mother follicular cells endowed with a high growth potential, may be different from mother follicles. For instance, the progeny of follicles may have a higher or lower iodine metabolism than their progenitor follicles. Some of the newly generated follicles have a high autonomous, i.e. TSH-independent, iodine turnover, while some others have a high autonomous growth potential. The degree of autonomous function is entirely independent of that of growth. In the process of goitrogenesis, newly generated follicles may, in addition, acquire new forms of expressing genetic functions. Such new traits, e.g. a particular growth pattern, may become inheritable and are then passed on from mother to daughter cells. The result is the most characteristic of all hallmarks of nodular goitres, which is the heterogeneity of structure and function between two diseased glands and even between closely adjacent follicles of the same gland. Greatly uneven intrinsic replication rates between different follicular cells and equally varying independency on growth stimuli account for regional differences in goitre growth. This, together with a network of fibrous scars interfering with unimpeded expansion of the growing follicle population, invariably produces a nodular growth pattern of the goitre. TSH certainly does not account for the growth of this type of goitre. Instead, a number of thyroid growth factors, including growth-stimulating immunoglobulins akin to those found in Graves' disease, have been discovered in recent years. Once the number of follicular cells with high intrinsic growth potential has become large enough under the impact of extrathyroidal growth stimuli, goitre growth may become autonomous and self-perpetuating. Whether or not a nodular goitre will produce thyrotoxicosis is a function of the number of follicles with high intrinsic iodine turnover which happen to be generated in the course of goitrogenesis. In contrast to thyrotoxicosis in Graves' disease, hyperthyroidism in nodular goitre is a very slowly progressing, insidiously evolving complication.

Childhood hyperthyroidism. Results of treatment

40 hyperthyroid children were followed for 0.2--12 (mean 4.5) years. The treatment was antithyroid drugs in 20, subtotal thyroidectomy after a drug trial in 18 and primary thyroidectomy in 2 patients. 4 patients who relapsed (3 after surgery and 1 after a drug trial) were given radioiodide. 11 of the surgically treated glands were nodular. At the follow-up study 24 patients were euthyroid, 7 were on thyroxine therapy and in 5 others hypothyroidism was discovered. 2 subjects were still on antithyroid drugs and 2 relapsed. In 5 euthyroid patients the TRH test revealed a low thyroid reserve. In 28 of 34 subjects examined circulating antibodies to thyroid microsomes were present in high titres. Evidently, regular follow-up is needed because of the high risk of hypothyroidism.