1192 system is set by the physicochemical characteristics of the binding protein or its concentration. There is ample evidence that changes in T.B.G. concentration do not lead to marked variations in FT4’ For these reasons we would not expect free hormone levels, where affinity of the hormone for its binding proteins is increased, to be raised, provided the subject is euthyroid. That our subjects with increased serum-T4 levels were euthyroid is suggested on clinical and other grounds and substantiated by normal T.R.H. test results for the propositi and by the fact that the mean basal T.S.H. of the group of affected subjects was normal. Last, but not least, the turnover of T4 in the propositi was also normal, which is to be expected when FT is normal. The decrease in distribution volume of T4 and the increase in the T pool is readily explained by the increased
ing biological
affinity. We agree with Ekins that the FT4 as measured with the commercial kit tends to be higher in those with increased T4 than in other relatives with normal T4. This increase is, however, moderate and not beyond the normal range, while the increases in FT4 indices are much greater and far above normal. In our paper the ratio between FT values for positive and negative members in family 1 is 1.32 and in family 2 it is 1.28. If the values are recalculated using the formula AxtT the ratio increases slightly in family 2, as Ekins records. Using,
however, the more complex expression:
found the following mean FT values for family 1: positive for trait 23.6, negative for the trait 18-7; ratio 1-26, and for family 2 (positive for trait 25-0, negative for trait 19.0; ratio 1.32). Normal FT4 values are (n=ll) 19.8 pmol/1 (s.D. 2.77). This calculation yields, in comparison with the original data, an FT4 ratio which is somewhat lower in family 1 and a little higher in family 2, but no systematic change seems to be apparent. We agree that FT4 measurements as estimated with equilibrium dialysis give higher values than those provided by the more modern methods mentioned by Ekins. Impurities of tracer may certainly have an effect. However, the mean dialysable fraction in the positive subjects (family 1 and 2 taken together) is 0.017% and in the negative relatives 0-031%. This difference cannot be explained on the basis of tracer impurity. The much lower values in the subjects with raised T, is conclusive evidence for increased affinity of T for binding proteins. The mean FT values as measured with this method in affected and unaffected members were almost identical, as mentioned in our letter of May 5 (p. 980). We believe that we have strong evidence that the increased T, in our subjects was caused by increased affinity of T, to serum binding proteins and that the affinity of T and rT are increased as well. Furthermore our patients are euthyroid with a normally functioning pituitary-thyroid axis. We suggest that the FT index does not reflect the thyroid status in these cases. There is no physiological basis for supposing that FT4 should be increased: on the contrary, we would expect this index to be normal. We agree that the commercial kit gives values which are somewhat higher in patients with raised T than in normal relatives, although these values are still normal. This increase is not explained, and we agree that it is important to perform "direct" free hormone measurements. If the increase recorded is indeed a true one the free T concept should be reconsidered. we
G. HENNEMANN R. DOCTER Departments of Internal Medicine and Clinical Endocrinology, Medical Faculty, Erasmas
University,
Rotterdam, Netherlands
III
E. P. KRENNING G. BOSS M. OTTEN
T. J. VISSER
HEPATITIS B VIRUS AND HEPATOCELLULAR CARCINOMA
SIR,-Dr Omata and colleagues and Dr Johnson (Feb. 24, p. 433, 434) question some aspects of our paper on the association between hepatitis B virus (H.B.v.) and hepatocellular carcinoma (H.c.c.).’ Omata et al. doubt whether Greeks are really representative of Europeans. As far as the prevalence of hepatitis B surface antigen (HBsAg) is concerned, they certainly are not. However, Greeks share with other Europeans an environment which is very different from that in Africa or Asia, where malnutrition, protozoal and other infections, and aflatoxin and other toxins-all of which may play a part in the aetiology of H.c.c.-are more
prevalent.
With some justification, Omata et al. also question the accuracy of our evaluation of the presence or absence of underlying liver disease (and in particular of alcoholic cirrhosis). However, our purpose was to evaluate the association ofH.B.v with H.C.C. in general, rather than with specific subgroups of it. If we had restricted our attention to H.c.c. with non-alcohohc liver disease, as Omata et al. suggest, the strength of the association (which should be evaluated with the relative risk or a similar index) would probably have been greater but it might have been less meaningful. To take an extreme example, if we had restricted our attention to patients with H.c.c. against a background of H.B v.-positive liver disease, the relative risk would have been infinite and meaningless. Johnson’ suggests that even if H.B.v. does cause cirrhosis and cirrhosis does lead to H.C.C. this is not a sufficient reason to indict H.B v. as a cause of H.c.c. Epidemiologists would disagree." If reduction of the H.B.v.-infection rate resulted in reduction of the incidence of H.C.C., then H.B.v. should be considered as a cause of H.c.c. no matter what the pathogenesis of H.C.C. turned out to be. Smoking is accepted as a cause of lung cancer although the pathogenesis has not been clarified and may be quite indirect. The W.H.O. suggested classification of deaths according to the "underlying" rather than the ’’immediate" cause reflects a similar philosophy. Johnson claims that "Studies confirming a relationship between active H.B.v. infection and H.C.C. in which such rigorous analysis is not carried out [i.e., demonstrating that proven non-cirrhotic H.C.C. patients have a significantly higher incidence of H.B.v. infection than. does a matched normal population] confirm only that H.B.v. is associated with cirrhosis and that cirrhosis may be complicated by H.c.c.". This statement would still be incorrect, even if the more appropriate term "prevalence" had been used for "incidence". Findings of this sort are compatible with either a direct or an indirect link between H.B-v. and H.c.c. The results of our own study are not conclusive in this respect, but other workers do not share Johnson’s conviction that cirrhosis is the only link between H.B.V. and H.c.c. Reed et a1.,4 for example, concluded their landmark paper on H.c.c. in Britain with the statement that "the association with H.B.v. cannot be simply explained by the occurrence of malignant change in the nodules of an HBAgpositive cirrhosis", and similar conclusions were reached by Prince et a1.5 and Kew et al.6 and by Szmuness’ in a review. Department of Hygiene and Epidemiology, University of Athens Medical School Goudi, Athens 609, Greece
D. TRICHOPOULOS
R. J., Xirouchaki, E., Sparros. L. Munoz, N. Lancet, 1978, ii, 1217. 2. MacMahon, B., Pugh, T. Epidemiology; p. 17. Boston, 1970. 3. Blalock, H. Causal Inferences in Nonexperimental Research, pp 3, 27 Chapel Hill, North Carolina, 1964. 4. Reed, W. D., Eddleston, A. L. W. F., Stern, R. B., Williams, R, Zuckerman. A. J., Bowes, A., Earl, P. M. Lancet, 1973, n, 690. 5. Prince, A. M., Szmuness, W., Michon, J, Demaille, J., Diebolt, G. Linhard. J. Quenum, C., Sankale, M. Int.J. Cancer, 1975, 16, 376. 6. Kew, M C., Marcus, R, Geddes, E. W. S. Afr. med. J. 1977, 51, 306 7. Szmuness, W. Prog. med Virol 1978, 24, 40.
1. Trichopoulos, D., Tabor, E., Gerety,
ing biological
affinity. We agree with Ekins that the FT4 as measured with the commercial kit tends to be higher in those with increased T4 than in other relatives with normal T4. This increase is, however, moderate and not beyond the normal range, while the increases in FT4 indices are much greater and far above normal. In our paper the ratio between FT values for positive and negative members in family 1 is 1.32 and in family 2 it is 1.28. If the values are recalculated using the formula AxtT the ratio increases slightly in family 2, as Ekins records. Using,
however, the more complex expression:
found the following mean FT values for family 1: positive for trait 23.6, negative for the trait 18-7; ratio 1-26, and for family 2 (positive for trait 25-0, negative for trait 19.0; ratio 1.32). Normal FT4 values are (n=ll) 19.8 pmol/1 (s.D. 2.77). This calculation yields, in comparison with the original data, an FT4 ratio which is somewhat lower in family 1 and a little higher in family 2, but no systematic change seems to be apparent. We agree that FT4 measurements as estimated with equilibrium dialysis give higher values than those provided by the more modern methods mentioned by Ekins. Impurities of tracer may certainly have an effect. However, the mean dialysable fraction in the positive subjects (family 1 and 2 taken together) is 0.017% and in the negative relatives 0-031%. This difference cannot be explained on the basis of tracer impurity. The much lower values in the subjects with raised T, is conclusive evidence for increased affinity of T for binding proteins. The mean FT values as measured with this method in affected and unaffected members were almost identical, as mentioned in our letter of May 5 (p. 980). We believe that we have strong evidence that the increased T, in our subjects was caused by increased affinity of T, to serum binding proteins and that the affinity of T and rT are increased as well. Furthermore our patients are euthyroid with a normally functioning pituitary-thyroid axis. We suggest that the FT index does not reflect the thyroid status in these cases. There is no physiological basis for supposing that FT4 should be increased: on the contrary, we would expect this index to be normal. We agree that the commercial kit gives values which are somewhat higher in patients with raised T than in normal relatives, although these values are still normal. This increase is not explained, and we agree that it is important to perform "direct" free hormone measurements. If the increase recorded is indeed a true one the free T concept should be reconsidered. we
G. HENNEMANN R. DOCTER Departments of Internal Medicine and Clinical Endocrinology, Medical Faculty, Erasmas
University,
Rotterdam, Netherlands
III
E. P. KRENNING G. BOSS M. OTTEN
T. J. VISSER
HEPATITIS B VIRUS AND HEPATOCELLULAR CARCINOMA
SIR,-Dr Omata and colleagues and Dr Johnson (Feb. 24, p. 433, 434) question some aspects of our paper on the association between hepatitis B virus (H.B.v.) and hepatocellular carcinoma (H.c.c.).’ Omata et al. doubt whether Greeks are really representative of Europeans. As far as the prevalence of hepatitis B surface antigen (HBsAg) is concerned, they certainly are not. However, Greeks share with other Europeans an environment which is very different from that in Africa or Asia, where malnutrition, protozoal and other infections, and aflatoxin and other toxins-all of which may play a part in the aetiology of H.c.c.-are more
prevalent.
With some justification, Omata et al. also question the accuracy of our evaluation of the presence or absence of underlying liver disease (and in particular of alcoholic cirrhosis). However, our purpose was to evaluate the association ofH.B.v with H.C.C. in general, rather than with specific subgroups of it. If we had restricted our attention to H.c.c. with non-alcohohc liver disease, as Omata et al. suggest, the strength of the association (which should be evaluated with the relative risk or a similar index) would probably have been greater but it might have been less meaningful. To take an extreme example, if we had restricted our attention to patients with H.c.c. against a background of H.B v.-positive liver disease, the relative risk would have been infinite and meaningless. Johnson’ suggests that even if H.B.v. does cause cirrhosis and cirrhosis does lead to H.C.C. this is not a sufficient reason to indict H.B v. as a cause of H.c.c. Epidemiologists would disagree." If reduction of the H.B.v.-infection rate resulted in reduction of the incidence of H.C.C., then H.B.v. should be considered as a cause of H.c.c. no matter what the pathogenesis of H.C.C. turned out to be. Smoking is accepted as a cause of lung cancer although the pathogenesis has not been clarified and may be quite indirect. The W.H.O. suggested classification of deaths according to the "underlying" rather than the ’’immediate" cause reflects a similar philosophy. Johnson claims that "Studies confirming a relationship between active H.B.v. infection and H.C.C. in which such rigorous analysis is not carried out [i.e., demonstrating that proven non-cirrhotic H.C.C. patients have a significantly higher incidence of H.B.v. infection than. does a matched normal population] confirm only that H.B.v. is associated with cirrhosis and that cirrhosis may be complicated by H.c.c.". This statement would still be incorrect, even if the more appropriate term "prevalence" had been used for "incidence". Findings of this sort are compatible with either a direct or an indirect link between H.B-v. and H.c.c. The results of our own study are not conclusive in this respect, but other workers do not share Johnson’s conviction that cirrhosis is the only link between H.B.V. and H.c.c. Reed et a1.,4 for example, concluded their landmark paper on H.c.c. in Britain with the statement that "the association with H.B.v. cannot be simply explained by the occurrence of malignant change in the nodules of an HBAgpositive cirrhosis", and similar conclusions were reached by Prince et a1.5 and Kew et al.6 and by Szmuness’ in a review. Department of Hygiene and Epidemiology, University of Athens Medical School Goudi, Athens 609, Greece
D. TRICHOPOULOS
R. J., Xirouchaki, E., Sparros. L. Munoz, N. Lancet, 1978, ii, 1217. 2. MacMahon, B., Pugh, T. Epidemiology; p. 17. Boston, 1970. 3. Blalock, H. Causal Inferences in Nonexperimental Research, pp 3, 27 Chapel Hill, North Carolina, 1964. 4. Reed, W. D., Eddleston, A. L. W. F., Stern, R. B., Williams, R, Zuckerman. A. J., Bowes, A., Earl, P. M. Lancet, 1973, n, 690. 5. Prince, A. M., Szmuness, W., Michon, J, Demaille, J., Diebolt, G. Linhard. J. Quenum, C., Sankale, M. Int.J. Cancer, 1975, 16, 376. 6. Kew, M C., Marcus, R, Geddes, E. W. S. Afr. med. J. 1977, 51, 306 7. Szmuness, W. Prog. med Virol 1978, 24, 40.
1. Trichopoulos, D., Tabor, E., Gerety,
