Hyperthyroidism and hypothyroidism in monozygotic twins: detection of stimulating and blocking THS receptor antibodies using the FRTL5-cell line

Recurrent Thyrotoxicosis due to Both Graves’ Disease and Hashimoto’s Thyroiditis in the Same Three Patients

Hashimoto's thyroiditis (HT) and Graves' disease (GD) are the 2 most common autoimmune disease processes affecting the thyroid gland. The relationship between the two is complex and not clearly understood. It has been theorized that HT and GD are 2 separate disease processes due to unique genetic differences demonstrated by genome studies. On the other hand, based on occurrence of both HT and GD in monozygotic twins and within the same family, they have been regarded to represent 2 ends of the same spectrum. This case report describes 3 patients who presented with thyrotoxicosis due to both GD and HT. The initial presentation was thyrotoxicosis due to GD treated with antithyroid medication followed by temporary resolution. They all subsequently experienced recurrence of thyrotoxicosis in the form of Hashitoxicosis due to HT, and then eventually all developed thyrotoxicosis due to GD, requiring radioablation therapy.

Prevalence of anti-Neu5Gc antibodies in patients with hypothyroidism

BACKGROUND

N-Glycolylneuraminic acid (Neu5Gc) is a sialic acid synthesized by animals, but not by humans or birds. However, it can be incorporated in human cells and can trigger immune response. In the present study, we detected anti-Neu5Gc antibodies in samples of the general population and of patients suffering from hypothyroidism/Hashimoto's disease, which is known to have autoimmune origin.

METHODS

Antibodies were measured using enzyme-immunosorbent techniques.

RESULTS

Serum anti-Neu5Gc IgG antibodies were higher in patients with hypothyroidism (mean: 14.8 ± 15.9 μg/mL, median: 10.0 μg/mL, P = 0.0003, Mann-Whitney) and even higher in the group with Hashimoto's thyroiditis (mean: 31.1 ± 16.3 μg/mL, median: 27.2 μg/mL, P = 0.0000, Mann-Whitney) compared to the general population (mean: 5.3 ± 4.7 μg/mL, median : 4 μg/mL). All anti-TPO positive samples had anti-Neu5Gc antibody concentration higher than the mean value of the general population while anti-TPO concentration was increased as anti-Neu5Gc concentration increased. Low concentrations of IgA and IgM antibodies were measured in both general population and patient groups.

CONCLUSION

The increased values of anti-Neu5Gc antibodies in patients with hypothyroidism/Hashimoto's disease and the correlation of anti-TPO incidence with increased anti-Neu5Gc concentration raise the possibility of an association between anti-Neu5Gc antibody development and autoimmune hypothyroidism.

Hashimoto's thyroiditis in childhood: presentation modes and evolution over time

Aim of this survey is to report the most recent views about Hashimoto’s thyroiditis (HT) natural history according to the different presentations. In children presenting with either euthyroidism or subclinical hypothyroidism HT spontaneous course is frequently characterized by a trend towards deterioration of thyroid function, whereas in those presenting with overt hyperthyroidism a definitive resolution of hyperthyroid phase is to be expected. Another possible even though unusual outcome of HT is the conversion to Graves’ disease.

Autoimmune thyroid diseases in children

The two major autoimmune thyroid diseases (ATDs) include Graves' disease (GD) and autoimmune thyroiditis (AT); both of which are characterized by infiltration of the thyroid by T and B cells reactive to thyroid antigens, by the production of thyroid autoantibodies and by abnormal thyroid function (hyperthyroidism in GD and hypothyroidism in AT). While the exact etiology of thyroid autoimmunity is not known, it is believed to develop when a combination of genetic susceptibility and environmental encounters leads to breakdown of tolerance. It is important to recognize thyroid dysfunction at an early stage by maintaining an appropriate index of suspicion.

Insufficient ketone body use is the cause of ketotic hypoglycemia in one of a pair of homozygotic twins

CONTEXT

Childhood ketotic hypoglycemia (KH) is a disease characterized by fasting hypoglycemia and increased levels of ketone bodies. The cause is unknown.

OBJECTIVE

The objective of the study was to study a pair of homozygotic twin boys, one of whom had severe KH from the age of 14 months, whereas the other boy was apparently healthy.

DESIGN AND RESULTS

At the age of 6 yr, the boys were thoroughly investigated. During a 24-h fasting tolerance test, the twin with KH showed hypoglycemia (blood glucose 2.0 mmol/liter) after 18 h. Three h before the occurrence of hypoglycemia, he had had 10 times higher beta-hydroxybutyrate levels than his brother, who showed no signs of hypoglycemia. Their glucose production rates were normal and similar (23.3 and 21.7 micromol/kg body weight per minute in the healthy and KH twin, respectively) as well as their lipolysis rates (5.8 and 6.8 micromol/kg body weight per minute, respectively). During repeated 60-min infusions of beta-hydroxybutyrate, the plasma level of beta-hydroxybutyrate increased 5-10 times more in the twin with KH (mean 1.1 mmol/liter in the healthy and 10.8 mmol/liter in the KH twin), indicating a disturbed clearance or metabolism of beta-hydroxybutyrate. No mutations were found in genes involved in ketone body metabolism or transport.

CONCLUSION

In the affected boy, KH seems to be the result of a reduced capacity to use ketone bodies, leading to increased peripheral metabolism of glucose that cannot be met by hepatic glucose production. Because the boys are homozygotic twins and only one of them is affected, the ketotic hypoglycemia is most likely caused by an altered imprinting of gene(s) involved in regulating metabolic pathways.

Premature twins of a mother with Graves' disease with discordant thyroid function: a case report

Thyroid dysfunction is recognized in the newborns of mothers affected by Graves' disease during pregnancy. We describe the development of concurrent hyperthyroidism and hypothyroidism in the twin infants of a mother with Graves' disease diagnosed during pregnancy.

Graves' disease and Hashimoto's thyroiditis in monozygotic twins: case study as well as transcriptomic and immunohistological analysis of thyroid tissues

OBJECTIVE

To report on the rare simultaneous occurrence of Graves' disease (GD) and Hashimoto's thyroiditis (HT) in monozygotic twins.

DESIGN

We compared the pattern of thyroid tissue-derived cDNAs to gain insight into previous and ongoing immune destruction and reconstruction processes using microarrays. The results were confirmed by immunohistology and real-time PCR.

RESULTS

Destruction of thyroid tissue in HT reduced levels of thyrocyte-related cDNAs and cDNAs encoding extracellular matrix components, but increased levels of proteases involved in extracellular matrix degradation compared with GD. Lymphocytic infiltrates forming ectopic follicles replaced the thyroid tissue almost completely in HT. Thus, lymphocyte-related cDNA levels were higher in HT than in GD. The same was true for many chemokines and their receptors, which not only enable migration towards the thyroid but also maintain the lymphocytic infiltrate. HT also showed increased levels of cDNAs encoding molecules related to apoptosis than did GD. Surprisingly, the Th1- and Th2-specific cytokine profiles suggested for HT and GD respectively could not be confirmed. cDNAs encoding factors and receptors involved in angiogenesis were increased in GD compared with HT.

CONCLUSIONS

Comparison of gene expression reflects the cellular differences between the two types of autoimmune thyroid disease in twins with identical genetic and similar environmental background.

Cytokine gene polymorphisms in autoimmune thyroid disease

Susceptibility to the autoimmune thyroid diseases, Graves' disease (GD) and autoimmune hypothyroidism (AIH), depends on a complex interaction between environmental and genetic factors. The human leukocyte antigen and cytotoxic T lymphocyte-associated-4 regions appear to influence susceptibility to disease, but the effect is not major, and the other genes remain unknown. Cytokines are crucial in the regulation of immune and inflammatory responses and therefore are potential candidate genes for autoimmune thyroid disease. In a case-control study, using a unified method of genotyping, we have examined 15 polymorphisms in 9 cytokine genes in 215 patients with autoimmune thyroid disease (GD, 138; AIH, 77) and 101 normal controls. Polymorphisms in the genes for interleukin-1alpha (IL-1alpha), IL-1beta, IL-1 receptor antagonist, IL-1 receptor 1, IL-4, IL-4 receptor, IL-6, IL-10, and transforming growth factor-beta were investigated. Genotyping was performed using the PCR and sequence-specific primers. Analysis showed a reduced frequency of the variant t allele in the IL-4 promoter polymorphism (position 590) in patients with GD and in the entire patient group (GD and AIH) compared with the control group [corrected P (Pc) = 0.00004 and Pc < 0.00001 for GD and all patients, respectively]. This was reflected in a reduction in the heterozygote genotype in the patient groups compared to the controls [c/t heterozygotes GD, 12%; Pc = 0.06, odds ratio, 0.4 (95% confidence interval, 0.2-0.7); all patients, 11%; Pc = 0.008; odds ratio, 0.4 (95% confidence interval, 0.2-0.7); control subjects, 23%]. There were no significant differences between the study groups for the other polymorphisms examined, and subgroup analysis revealed no association with clinical parameters of disease. These results suggest that an IL-4 variant or a closely linked gene has a modest protective effect against the development of autoimmune thyroid disease, particularly GD. This variation in the IL-4 gene may provide further clues to the pathogenesis of autoimmune thyroid disease and other organ-specific autoimmune diseases. Furthermore, these results suggest that subtle variation in immunoregulatory genes may be associated with autoimmune disease states.

Presence of thyrotropin receptor in infant adipocytes

In healthy infants, the levels of TSH are known to peak at 50-100 times adult values during the first days of life. In studies of isolated human infant adipocytes, we have earlier shown that bovine TSH (bTSH) has a strong lipolytic effect, accompanied by a blunted response of adipocytes to catecholamines. In this study, we used human recombinant TSH (hTSH), and incubation of adipocytes with hTSH induced a lipolytic response similar to that obtained with the beta-adrenergic receptor agonist isoprenaline in adipocytes isolated from three infants. The lipolytic effect of hTSH was completely blocked by inhibitory TSH receptor (TSHR) antibodies. The TSHR mediates the effects of TSH in the thyroid, and it has been detected in some extrathyroid tissues, but not in isolated human adipocytes or childhood adipose tissue. In this study, we found TSHR RNA in infant and adult adipose tissues and isolated adipocytes with reverse transcriptase-PCR. The sequence of the amplified PCR product agreed with the published sequence. Northern blot hybridization on RNA prepared from infant adipose tissue showed a transcript of the expected size, and the expression of TSHR seemed higher in infant than in adult adipose tissue. In conclusion, this study indicates that TSH plays an active role in the metabolic adaptation after birth.

The IgG subclass distribution of TSH receptor blocking antibodies in primary hypothyroidism

OBJECTIVE

TSH receptor stimulating antibodies are restricted to the IgG1 subclass suggesting an oligoclonal origin. We wished to determine whether thyroid stimulation blocking antibodies, which also bind to the TSH receptor but may cause hypothyroidism, are similarly IgG subclass restricted.

DESIGN

Sera containing TSH receptor blocking antibody activity were separated into IgG subclasses by negative depletion of all other subclasses on affinity columns of subclass-specific monoclonal antibodies or protein A as appropriate.

PATIENTS

Eleven patients from two centres were studied. All had autoimmune hypothyroidism and TSH receptor blocking antibodies but no thyroid stimulating antibodies.

MEASUREMENTS

TSH receptor blocking antibody activity was measured by assessing inhibition of TSH-stimulated cAMP production by human thyroid cells (five Israeli samples) or by the FRTL-5 rat thyroid cell line (six Korean samples).

RESULTS

IgG1 was the most important subclass containing TSH receptor blocking antibody activity but complete restriction to this subclass was never seen. Clearly detectable activity was found in the IgG2 subclass in eight patients, in the IgG3 subclass in three patients, and in the IgG4 subclass in six patients. The percentage recovery of activity in the sum of the separated fractions generally corresponded to the activity in whole immunoglobulin, being 117 +/- 66% in the nine patients in whom this could be assessed, although in one of these, the activities in the sum of the fractions was much higher (284%).

CONCLUSIONS

Unlike thyroid stimulating antibodies, thyroid stimulation blocking antibodies are not subclass restricted and are therefore likely to have a polyclonal origin. The IgG subclass distribution of these blocking antibodies resembles that of thyroglobulin and thyroid peroxidase antibodies.

Can autoimmune mechanisms account for the genetic predisposition to schizophrenia?

Applications of molecular genetic techniques to schizophrenia have shown great initial promise but have then proved disappointing. In order to maximise chances of elucidating the genetic mechanism underlying schizophrenia, diverse strategies and diverse perspectives must be adopted. Most studies begin with the premise that, although schizophrenia may be a heterogeneous collection of diseases, some subtypes will be primarily single-gene disorders. We are concerned that this single-gene hypothesis may be incorrect. Schizophrenia research may benefit from application of knowledge from other disciplines and from other diseases which, in terms of epidemiology and apparent genetic mechanisms, bear some resemblance to schizophrenia.