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The thyroid gland is immunologically privileged
In a negative sense, of course. Perhaps because it is so strongly linked
with the environment, we do see in our out-patient departments so many
hypothyroid patients with the sequelae of several kinds of thyroid autoimmune
derangement. Although we can sometimes see the sequelae of an autoimmune
adrenalitis as a cause of Addison's disease (tuberculous lesions being
the chief cause in the past), the patients with sequelae of the autoimmune
thyroiditis are much more common than the patients with sequelae of the
autoimmune adrenalitis. What is more, the Graves' disease, caused by an
autoimmune thyroid-stimulating antibody (thyroid-stimulating immunoglobulin,
TSI) is an important point. TSI was the first antibody possessing hormonal
function to be discovered. So we encounter not only autoimmune thyroid
hypofunction, but also thyroid hyperfunction, caused by an autoimmune mechanism.
Although ASI (adrenal stimulating immunoglobulin) may also exist as a cause
of Cushing's syndrome, TSI-induced Graves' disease is much more common.
The unresolved linkage with stress - an immunosuppression by the stress
hormones (CRH, glucocorticoids) in the sense of anti- antibodies - when
antibodies to TSI are suppressed is another enigma.
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