CHRONIC HEPATITIS B INFECTION AND AUTOIMMUNE THYROIDITIS IN DOWN SYNDROME

Philip May, M.D. Clinical Associate Professor of Medicine UMDNJ - Robert Wood Johnson Medical School New Brunswick, NJ Attending Physician Developmental Medicine Clinic Department of Internal Medicine Staff Physician Hunterdon Developmental Center Clinton, NJ

*Hidenori Kawanishi, M.D., Ph.D. Professor of Medicine UMDNJ - Robert Wood Johnson Medical School New Brunswick, NJ

Address correspondence to: Philip May, M.D. Medical Department Hunterdon Developmental Center Box 4003 Clinton, NJ 08809. Phone (908) 735-4031 FAX (908) 730-1322

* Current Address Chairman, Department of Medicine Professor in Residence Kameda Foundation and Medical Center 929 Higashi-Machi Kamogawa City, Chiba 296, Japan

The study reported here was undertaken to further examine the relationship of thyroiditis and hepatitis, using a series of patients with Down syndrome and comparing them with an age, sex, and environmentally matched control group of mentally retarded patients without Down syndrome. If such a relationship could be demonstrated, this might provide insight into basic immunopathologic mechanisms that could generalize to other populations.

METHODS: The study group consisted of mentally retarded residents of the Hunterdon Developmental Center, Clinton, N.J., a State "ICF/MR" residential facility housing 645 severely and profoundly mentally retarded individuals. There were 57 residents with Down Syndrome (DS) and 588 residents without Down syndrome (NODS). Of the DS group, there were 42 males (74%) and 15 (26%) females. The mean age of the DS group was 33 years with a range of 22-61 years (Table 1, SEE BELOW).

TABLE 1: COMPARISON OF AGE AND SEX CHARACTERISTICS OF MENTALLY RETARDED PATIENTS WITH (DS) OR WITHOUT(NODS) DOWN SYNDROME WHO HAD COMPLETE THYROID TESTS. p>0.05 for age and sex.

Al1 subjects in the DS group were tested for hepatitis B and thyroid function (see below). Of the 588 NODS group all were tested for hepatitis B. Four hundred fifty chosen at random and all of the hepatitis B carriers had complete thyroid tests (Table 1). Of the 450 with complete thyroid tests, there were 286 males (64%) and 164 females (36%). The mean age of the NODS group with complete tests was 34 years with a range of 18-83 years. The age and sex characteristics of the DS group were not significantly different from the NODS group.

There was no significant difference between the I.Q.'s of the DS and the NODS groups. Etiologies of cognitive impairment in the NODS group were multiple and included phenylketonuria, tuberous sclerosis, neurofibromatosis, fragile X syndrome, various infections, and traumas, but the majority of the cases were of unknown etiology.

Fasting venous blood samples were obtained for all laboratory determinations. The following tests were performed through our clinical referral laboratory (SmithKline Beecham Clinical Laboratories, Norristown, PA): Thyroxine (normal 4.5 - 12.5 microgram %), Triiodothyronine (normal 85 - 185 micrograms %), T3 resin uptake (normal 25 - 35%), and TSH (normal 0.3 - 5.0 microunits/ml). These were determined by standard radioimmune techniques utilizing commercial kits supplied by Ciba-Corning. Antimicrosomal (normal less than 1:100) and antithyroglobulin antibodies (normal less than 1:10) were detected by hemagglutination utilizing kits supplied by Wellcome Diagnostics. Hepatitis B surface antigen (normal ratio 0.00 - 7.70) was determined by Elisa Enzyme Immuassay from kits supplied by Abbott Laboratories. Other viral markers including hepatitis B viral DNA, e antigen and antibody, IgG and IgM core antibody, hepatitis A antibody, and Hepatitis C antibody were determined in all hepatitis B carriers with and without Down syndrome by our reference laboratory (SmithKline Beecham) using standard methodology.

"Thyroid disease" was defined as (a) positive antithyroid antibodies alone or associated with low T4 and/or elevated TSH, (b) persistent TSH elevation above 10 microU/ml alone or associated with low T4 and/or positive antithyroid antibodies, (c) distinctly elevated T4 and T3. It was decided to use this definition of "thyroid disease" rather than "autoimmune thyroiditis" because it is well-known that serum thyroid antibodies can fluctuate and at times disappear (11) and may therefore not reflect the histopathological diagnosis. There was only one case of Down syndrome that clearly had "thyroid disease" (low T4, elevated TSH) who did not have positive antithyroid antibodies at the time of testing. Therefore in Down syndrome "thyroid disease" is virtually synonymous with "autoimmune thyroiditis" (see below under "discussion"). Statistical significance was determined by Chi Square analysis for discrete data.

RESULTS: Mild reductions of T4 and T3 levels secondary to anticonvulsant medication and/or illness were common and were not considered to represent thyroid disease. Isolated transient slight elevations of TSH above normal, but less than 10 microU/ml were also seen and were not felt to represent thyroid dysfunction.

Thirty-nine percent of patients with Down syndrome met the criteria for thyroid disease while, of the 450 NODS group with complete thyroid tests, only 7% met the criteria for thyroid disease (Table 2, SEE BELOW).

TABLE 2: FREQUENCY OF THYROID DISEASE IN MENTALLY RETARDED PATIENTS WITH DOWN SYNDROME VERSUS NO DOWN SYNDROME. THE FREQUENCY OF THYROID DISEASE WAS SIGNIFICANTLY GREATER FOR THE DOWN SYNDROME GROUP.

Thirty percent of the DS group gave a history of greater than one year positivity for the Hepatitis B surface antigen, while the same was true for only 6% of the NODS group (Table 3, SEE BELOW).

TABLE 3: FREQUENCY OF HEPATITIS B CARRIER STATE IN MENTALLY RETARDED PATIENTS WITH AND WITHOUT DOWN SYNDROME. THE FREQUENCY OF HEPATITIS B CARRIER STATE WAS SIGNIFICANTLY GREATER FOR THE DOWN SYNDROME GROUP.

Of the DS individuals who were HB carriers, sixty-five percent had thyroid disease compared to only a twenty three percent incidence of thyroid disease in those DS patients who were not Hepatitis B carriers (fig. 1, SEE BELOW).

FIGURE 1: EFFECT OF HEPATITIS B CARRIER STATE (HBC) ON THE FREQUENCY OF THYROID DISEASE WITH AND WITHOUT DOWN SYNDROME. (p>0.05 for age and sex).

There was no effect of the Hepatitis B carrier state on the frequency of thyroid disease in those mentally retarded individuals without Down syndrome (fig. 1).

There was no significant difference between the DS and NODS groups in the incidence of natural immunity to HBS Ag (49% vs 48%) (Table 4, SEE BELOW).

TABLE 4: COMPARISON OF INITIAL HEPATITIS B "STATUS" IN PATIENTS WITH AND WITHOUT DOWN SYNDROME.

There was no significant difference between the DS vs NODS groups in the prevalence of viral markers other than HBS Ag (Table 5, SEE BELOW.)

TABLE 5: PREVALENCE OF VIRAL MARKERS OTHER THAN HBsAg IN CHRONIC HBsAg CARRIERS WITH AND WITHOUT DOWN SYNDROME.

There was no effect of viral DNA, e-antigen, surface antigen titer, hepatitis A antibody, or hepatitis C antibody on the prevalence of thyroid disease in those Down syndrome patients who were carriers of hepatitis B surface antigen, although one of the two DS with positive viral DNA had thyroid disease, while none of the six NODS with positive viral DNA had thyroid disease.

DISCUSSION: Autoimmune phenomena that are known to complicate viral hepatitis includes arthritis, glomeruionephritis, periarteritis nodosa, serum-sickness-like syndrome, essential mixed cryoglobulinemia, and various skin rashes (12). While it has been suggested that thyroiditis might also be associated with viral hepatitis, the evidence for this in humans is not well established. An increased incidence of thyroid antibodies is known to occur following acute infectious hepatitis (13), and there are data to suggest hepatic mitochondrial antigens can activate thyroid gland destruction (14). Recently it has been reported that thyroid autoimmunity frequently occurs in association with hepatitis C. Furthermore, thyroiditis can be exacerbated in patients with hepatitis C who are treated with interferon (15).

While it has been established that thyroid dysfunction frequently occurs in Down syndrome, its pathogenesis is poorly understood. Autopsy studies have demonstrated that chronic thyroiditis is present in virtually all cases of Down syndrome (3- 5). In addition, clinical laboratory testing has revealed a high frequency of abnormal results when thyroid function has been tested in Down syndrome (6-8). Positive antithyroid antibodies and elevated Thyroid Stimulating Hormone (TSH) are the most frequently encountered abnormalities. Additional studies have demonstrated abnormalities in T cell numbers or function. Others have reported a possible relationship between thyroid dysfunction in Down syndrome with infectious hepatitis (13), and hepatitis B (10).

Finally, certain cytokines (known to be released during active hepatitis), have been demonstrated to induce aberrant histocompatibility antigens in thyroid cells, and might then, therefore be responsible for cellular immunity directed against the thyroid gland (16, 17).

It is unclear why chronic hepatitis B antigenemia should only be associated with autoimmune thyroiditis in Down syndrome and not in other mentally retarded or otherwise "normal" people.

The study reported here suggests that chronic exposure to hepatitis B surface antigen (but not actively replicating virus) might lead to autoimmune thyroid disease in Down syndrome.

Alternatively, initial exposure to hepatitis B virus in Down syndrome miqht result in an interferon-mediated "supersensitive'· immune response, leading to acute release of hepatic antigen into the blood stream and rapid clearing of the hepatitis virus. Those Hepatic antigens released during the initial immune response might sensitize T cells to cross react with thyroid cell antigens and lead to thyroiditis. This hypothesis is consistent with the observation that most Down syndrome carriers are of the "healthy" type and do not possess viral DNA, e antigen, or elevated liver enzymes (Table 5).

Additional support for this hypothesis comes from studies which demonstrate that liver mitochondrial antigens can elicit a positive Leukocyte Migration Inhibition test in patients with thyroiditis, but not in controls without thyroiditis. The authors interpret the data as evidence that hepatic antigens can activate thyroid directed T-cells which might then lead to thyroid destruction (14). Residual circulating hepatitis B surface antigen may therefore only represent a "marker" and not be of etiologic importance in the development of thyroiditis.

It has been previously suggested that interferon, a lymphokine known to induce aberrant Major Histocompatibility Complex (MHC) Class II antigen expression by thyroid cells, may play an important role in the development and/or maintenance of thyroid autoimmunity. Since interferon receptors are coded for by genetic material on chromosome 21, thyroid cells in Down syndrome should have 1.5 times the normal dose of interferon receptors (19) and should therefore be more sensitive to antigen inducing effects of interferon. Although there is evidence that "acute" interferon production may be impaired in DS (20) thus explaining the propensity to viral carrier state development, it is possible that "chronic" exposure to agents such as the hepatitis B virus may eventually stimulate secretion of cytokines that might then predispose to thyroid antigen induction on interferon sensitive DS thyroid cells. In support of this concept, it has previously been shown that thyroid dysfunction can occur during administration of interferon alone or combined with interleukin II (17). It is thus plausible that cytokines may play a role in the development of thyroi.d dysfunction in Down syndrome.

Finally, from a clinical perspective, it is suggested that patients with Down syndrome should be immunized against hepatitis B and immunity should be documented by periodic serum antibody titer determination. Furthermore, Down syndrome patients who are also hepatitis B carriers should be closely monitored for development of thyroid disease.

REFERENCES:

l. Breg W. Down Syndrome: A Review of Recent Research in Proaress Pathobiol. Annu. 1977; 7: 257-303

2. Hollinger F., Goyal R., Hersh T., Powell H., Schulman R., Melnick J. Immune Response to Hepatitis Virus Tvpe B in Down's Syndrome and other Mentally Retarded Patients: Am J. of Epidemiology 1972; 95: 356-362.

3. Benda, C.E., Studies in Mongolism II. The Thyroid Gland, Arch.Neurol. Psychiat. 1939; 41: 243-259.

4. Benda, C.E., Endocrine Aspects of Mongolism, J. Clin. Endocrinol 1942; 2: 737-748.

5. Benda, C.E., The Child with Mongolism, NY and London: Grune and Stratton; 1960.

6. Hollingsworth D., McKean H., Roeckel I. Goiter, Immunological Observations and Thyroid Function Tests in Down Syndrome Am J Dis Child. 1974; 127: 524-527.

7. Friedman D., Kastner T., Pond W., O'Brien D. Thyroid Dysfunction in Individuals with Down Syndrome Arch Int Med. 1989; 1949; 1990-1993.

8. May P. Thyroid Dysfunction in Down Syndrome: Relationship with Hepatitis B Carrier State. Abstract Book, AAMR Annual Meeting Washington DC,115th May 19-23, 1991, Abstract: p.52

9. Fialkow P., Blumberg B., London W., Sutnick A., Thuline H. Thyroid Antibodies and Australia Antigen in Down's Syndrome. J. Ment Defic Res. 1971; 15: 177-180.

10. Ugazio A., Jayakas S., Marcioni A., Duse M., Monafo V., Pasquali F., Burgio G. Immunodeficiency in Down's Syndrome: Relationship between Presence of Thyroglobulin Antibodies and HBsAg Carrier Status. Europ J Pediat. 1977; 126: 139-146.

11. Tunbridge W. The Epidemiology of Hypothyroidism. Clinics in Endocr. & Metab. 1979; 8: 21-27.

12. Zakim D., Boyer T. Nonhepatic Disorders in Viral Hepatitis Believed to be Mediated by Circulating Immune Complexes. Hepatology: A Textbook of Liver Disease (1990), W.B. Saunders Co., Publishers, p.p. 981-1016.

13. Dellaire L., Kingsmill-Flynn D., Leboeuf G. Thyroid Autoantibodies in Relation to Infectious Hepatitis and Down's Syndrome. J. Ment Defic Res. 1968; 12: 93-99.

14. Wartenberg J., Doniach D., Brostoff J., Roitt I. Leucocyte Migration Inhibition with Mitochondria in Human Autoimmune Thyroid Disorders. Clin Exp Imunol. 1973; 14: 203-212.

15. Preziati D., Autoimmune Thyroid Disease in Patients with Chronic Active Hepatitis Treated with Interferon Alpha-2a. Europ J of Endocrin. 1995; 132: 587-593.

16. Utiger R. The Pathogenisis of Autoimmune Thyroid Disease N Engl J Med. 1991; 325: 278-279.

17. Schwartzenruber D. Thyroid Dysfunction due to Interleukin-2 in the Treatment of Cancer. Cancer 1991; 68: 2384-2390.

18. Wisniewski K., Cobill J., Wilcox C., Caspary E., Williams D., Wisniewski H. T Lymphocytes in Patients with Down's Syndrome Biological Psychiatry 1979; 14: 463-471.

19. Epstein C.J. The Consequences of Chromosome Imbalance. Principles, Mechanisms, & Models. (1986), New York: Cambridge University Press.

20. Boyer J., Fontes A., Interferon Levels in Down's Syndrome. Journal Am Osteo Assoc. 1975; 437: 132-139.

21. Weber P., Wiedmann K.H., Klein R., Walter E., Plum H., Berg P. Indications of Autoimmune Phenomena in Patients with Chronic Hepatitis B Treated with Gamma Interferon, Journal of Hepatology 1994; 20: 321-328.