Endemic goitre in Greece: a study of 379 twin pairs.

Non-toxic goitre is endemic in Greece (Malamos Koutras, Kostamis, Kralios, Rigopoulos, and Zerefos, I966a), and detailed biochemical studies have implicated iodine deficiency as the main causative factor (Malamos, Miras, Koutras, Kostamis, Binopoulos, Mantzos, Levis, Rigopoulos, Zerefos, and Tassopoulos, I966b). However, in the endemic regions studied, both goitrous and non-goitrous persons are iodine deficient practically to the same extent (Malamos et al., i966b), which agrees with results in other parts of the world (Wayne, Koutras, and Alexander, i964), most notably in Western New Guinea (Choufoer, van Rhijn, Kassenaar, and Querido, I963). This has prompted a search for additional factors which predispose a part ofthe population to goitre development, or to put it in another way, which protect the other from it. It is now recognized that some cases of sporadic goitre, with or without cretinism, are due not to iodine deficiency but to inherited defects in the biosynthesis of thyroid hormones (McGirr, I960; Stanbury, I966; Wayne et al., I964). None of these defects has been proved to occur in endemic goitre (Murray and Stanbury, i962), and a careful search in Greece has not produced evidence that any of these is of importance in the aetiology of the goitrous endemic (Malamos et al., I966b). Nevertheless, since the environmental factor of iodine deficiency does not explain entirely the development of endemic goitre, this has revived interest in the possible implication of genetic factors, which may potentiate the effects of a mild environmental iodine deficiency. Hadjidakis, Koutras, and Daikos (I964) have shown that in Greece endemic goitre affects some families more than others from the same yillage. This has been interpreted as evidence of an inherited factor, though the influence of the small family environment cannot be excluded. In a subsequent study by Malamos et al. (i966a) the familial aggregation of goitrous cases has been confirmed. However, it has been found that not only are the progeny of goitrous persons more extensively affected than the descendants of nongoitrous parents, but also that there is a statistically significant concordance between husbands and wives. Women married to goitrous men are themselves more often goitrous than the wives of the non-goitrous inhabitants of the same village. This, of course, points to the small family environment rather than to heredity as the cause of the familial aggregation of cases. In view of these inconclusive findings, the present investigation was undertaken. 379 twin pairs from the endemic regions of central Greece were examined for the presence or absence of goitre, and the results were analysed separately for the monozygotic and the dizygotic twins, in order to find out whether there was a higher concordance in the former, as would be expected if goitre was an inheritable characteristic.