Endemic goiter in Greece: thyroid hormone kinetics

Differentiated thyroid cancer: a retrospective analysis of 832 cases from Greece

OBJECTIVE

To analyse the initial manifestations, pathological findings, therapy, outcome and prognostic factors in patients with papillary and follicular carcinoma.

PATIENTS

832 patients with well differentiated thyroid carcinoma managed in our department during a period of 30 years (1965-1995). Follow-up data were available for 609 patients for a mean of 5.5 years (range 1-38 years), the remainder having been lost to follow-up.

RESULTS

The patients were 677 (81%) with papillary and 155 with follicular carcinoma. They were predominantly female (75%), presenting mainly with a single nodule (53%), while at the time of diagnosis 72% had intrathyroidal carcinomas (class I), 17% had nodal metastases (class II), 7% soft tissue invasion (class III) and 4% distant metastases (class IV). Fifty-five percent of the patients had a complete thyroidectomy (36% had a near total or total thyroidectomy and 19% near total or total thyroidectomy plus block dissection), 2.6% received external radiotherapy and 94% had radioactive iodine as part of the treatment of the original disease. Kaplan-Meier survival analysis was used to calculate both cancer related mortality and disease free survival in the patients followed-up. Although mortality (21 cancer-related deaths) was slightly higher for follicular than papillary carcinoma (10% vs. 5% and 16% vs. 10% in 10- and 15-year survival, respectively) the difference was not statistically significant. Extent of disease at diagnosis, male sex, tumour size and age > 60 years affected probability of cancer death. Cox's proportional hazard regression analysis for disease free survival showed that adverse independent prognostic factors were, for papillary carcinoma, male sex, class II or higher, tumour size > 1 cm and age > 60 years, while for follicular, class III or higher, size > 4 cm and age > 40 years.

CONCLUSIONS

We conclude that there is a higher prevalence of follicular carcinoma in our country probably due to a moderate degree of iodine deficiency still existing in Greece. Age and extent of disease at diagnosis were important prognostic factors affecting morbidity and mortality, whereas sex, tumour features and histological type were of minor importance. All these prognostic factors and their relative importance should be taken in consideration in the management of this disease.

The TRH stimulation test in endemic goitre in Greece

The serum T4=T4(D), T3 in vitro uptake=RT3U and TSH were measured before and 30 min after the injection of 200 mug of TRH in 30 subjects from an iodine deficient area of Central Greece. These persons were divided in two groups of 16 goitrous and 14 nongoitrous patients and the results from each group compared to each other and also with the same parameters obtained from 14 controls subjects, all nongoitrous and from a nonendemic area. It has been found that in this area with a mild iodine deficiency serum T4 is the only hormone decreased whereas RT3U and TSH both before and 30 min after TRH injection are normal. There existed however a negative correlation between serum T4 and TSH in the goitrous group. Why the nongoitrous iodine deficient persons achieve the same compensation without thyroid gland enlargement remains unsolved but it may be stated from the present results that goitre development should be regarded as a maladaptation rather than a compensatory process.

The use of lithium in the treatment of thyrotoxicosis

Since lithium has been shown to inhibit release of iodine from the thyroid, we have investigated its therapeutic potential in thyrotoxicosis. Eight detailed (131)I kinetic studies were performed on seven thyrotoxic women and data was analyzed using a computer program. Lithium at serum levels of about 1 mEq liter decreased the loss of (131)I from the thyroid, led to a fall in serum (131)I levels and diminished urinary (131)I excretion. Computer simulation of the lithium effect required, in every case, that lithium inhibit hormonal and nonhormonal thyroid iodine release. In five cases a second lithium effect was required for a satisfactory fit of the model soluton with observed data: namely, an inhibition of hormone disappearance from serum. NEITHER INHIBITION OF RELEASE NOR OF HORMONE DISAPPEARANCE SEEMED TO BE AFFECTED BY METHIMAZOLE (RELEASE: 52% decrease without methimazole, 60% with methimazole; hormone disappearance: approximately 60% decrease in both). When Li(+) was discontinued, recovery of the iodine release rate and hormone disappearance rate over the observed time span was variable, ranging from no recovery to rates that exceeded pre-Li(+) values. When Li(+) is used alone its effect on serum hormone levels is diminished due to continued accumulation of iodide by the thyroid. Thus, serum thyroxine-iodine levels fell 21-30% in 6-8 days in patients who did not receive methimazole and 15-67% in the methimazole-treated subjects. For prolonged therapy, therefore, a thiocarbamide drug must be used in conjunction with Li(+). The similarity of inhibition of iodine release from the thyroid produced by Li(+) and iodides is discussed.

Simultaneous measurement of thyroxine and triiodothyronine peripheral turnover kinetics in man

Serum triiodothyronine (T(3)) kinetics in man have been difficult to define presumably due to the interference of iodoproteins generated during the peripheral metabolism of T(3). The use, in the present study, of an anion-column chromatographic method for separation of serum T(3) as well as thyroxine (T(4)) from these iodoproteins has overcome this technical handicap. Simultaneous measurement of serum (125)I-T(3) and (131)I-T(4) kinetics were performed in 31 subjects from the clinical categories of euthyroid, primary hypothyroid, thyrotoxic and posttreatment hypothyroid Graves' disease, factitial thyrotoxic, and idiopathically high and low thyroxinebinding globulin states. The normal mean T(3) fractional turnover rate (kT(3)) was 0.68 (half-life = 1.0 days), increased in toxic Graves' disease patients to 1.10 (half-life = 0.63 days), and decreased in primary hypothyroid patients to 0.50 (half-life = 1.38 days). The mean T(3) equilibration time averaged 22 hr except in hypothyroid and high thyroxine-binding globulin (TBG) patients where the equilibration period was delayed by 10 hr. The mean T(3) distribution space in normal subjects was 38.4 liters. This was reduced in subjects with high TBG levels (26 liters) and increased in patients with low TBG and in all hyperthyroid states (53-55 liters). The normal serum T(3) concentration was estimated by radioimmunoassay to be 0.106 mug/100 ml. Combined with the mean T(3) clearance value of 26.1 liters/day, the calculated T(3) production rate was 27.6 mug/day. The mean T(3) production rate increased to 201 mug/day in thyrotoxic Graves' disease patients and was reduced to 7.6 mug/day in primary hypothyroid subjects. T(3) production rate was normal in subjects with altered TBG states. The ratio of T(3) to T(4) production rate in normal subjects was 0.31 and was unchanged in patients with altered TBG values. This ratio was increased in all Graves' disease patients with the highest value being 0.81 in the posttreatment hypothyroid Graves' disease group. This apparent preferential production of T(3) may have been responsible for the retention of rapid turnover kinetics for T(3) and T(4) observed in treated Graves' disease patients. The finding that factitial thyrotoxic patients also displayed similar rapid T(3) and T(4) turnover kinetics indicates that these alterations are not a unique feature of Graves' disease per se. When comparing the peripheral turnover values for T(3) and T(4) in man, it is apparent that alterations in metabolic status and serum TBG concentration influence both hormones in a parallel manner; however, changes in metabolic status seem to have a greater influence on T(3) kinetics while alterations in TBG concentrations have a greater effect on T(4). These observations probably relate to the differences in TBG binding affinity and peripheral tissue distribution of these two hormones.