Thyroid diseases thyroiditis population

It is difficult to define the normal range of iodine intake in humans, and despite efforts to provide iodine supplementation in many geographic areas of the world, endemic iodine deficiency and attendant goiter remain a world health problem (147). Exposure to excess iodine may sometimes lead to the development of thyroid disease. This unusual type of iodide-induced goiter has been found, for example, in 10% of the population of a Japanese island where fishermen and their families consume large quantities of an iodine-rich seaweed and have an iodine intake as high as 200 mg/d (148). 

Many environmental factors have been implicated in the induction of autoimmunity. One dietary component, iodine, has been well studied as a factor that increases autoimmune thyroid disease.67 68 Based on studies in the OS chicken, the increasing prevalence of autoimmune thyroid disease observed in U.S. and Western European populations has been ascribed to increased use of iodized salt.69 Experimentally, it can be shown that iodinated thyroglobulin is a more potent autoantigen than the equivalent noniodinated molecule. Food additives or pesticides may also be important in contributing to the development of autoimmune disease in susceptible individuals.70... 

From the results of the variety of studies undertaken, it now appears certain that no one single immunological factor is responsible for the various forms of heart diseases which are seen in populations in subtropical and tropical countries. Thus, in patients with endomyocardial fibrosis (EMF), rheumatic heart disease, or idiopathic cardiomegaly, heart antibodies were present in 42% and thyroid antibodies in 15% serum cryoglobulins were present in 74% of the patients but was more frequent in those patients who had EMF than in any of the other groups (VI). The suggestion was therefore made that patients with EMF were... 

In the adult population, the prevalence of overt hypothyroidism is 19 per 1000 women and 1 per 1000 men with annual incidence of overt hypothyroidism is 4 per 1000 women and 0.6 per 1000 men. Subclinical hypothyroidism is also more common in women, the incidence increases with age, with up to 10% of women older than 60 years having an increased thyroid-stimulating hormone concentration. Subclinical hypothyroidism is more common in people who have been treated for hyperthyroidism with radioactive iodine or surgery, and in those with organ-specific autoimmune diseases, such as pernicious anaemia, type 1 diabetes mellitus, or Addison s disease. 

Interferons are contraindicated in individuals with autoimmune hepatitis or other autoimmune disease, uncontrolled thyroid disease, severe cardiac disease, severe renal or hepatic impairment, seizure disorders, and CNS dysfunction. Immunosuppressed transplant recipients should not receive interferons. Interferons should be used with caution in persons who have myelosuppression or who are taking myelosuppressive drugs. Preparations containing benzyl alcohol are associated with neurotoxicity, organ failure, and death in neonates and infants and therefore are contraindicated in this population. Interferons should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. 

Iodine should be given to the general population if the risk of radioiodine exposure is sufficient (over 15-100 rem), but people with increased susceptibility to the adverse effects of iodine (previous thyroid disease or known serious allergies) should be excluded (11-16). In elderly people the benefit of stable iodine probably does not outweigh its potential adverse effects, while in pregnant women and infants the benefit to harm balance is not established rapid evacuation of such people from fallout zones should be given the highest priority (SEDA-11, 358). 

The immunological predisposition to thyroid disorders has been studied in 17 of 439 Japanese patients who had symptomatic autoimmune thyroid disorders during interferon alfa treatment (521). There was a significantly higher incidence of the human leukocyte antigen (HLA)-A2 hap-lotype compared with the general Japanese population (88 versus 41%), suggesting that HLA-A2 is a possible additional risk factor for the development of interferon alfa-induced autoimmune thyroid disease. 

While hypofunction of the thyroid gland is relatively common, hyperfunction is an uncommon illness affecting less than 0.25 percent of the population. It is more prevalent among females than males (8 1) and usually occurs in middle age it rarely occurs in children or adolescents. Hyperfunction of the thyroid gland is known as Graves disease, after the Irish physician who was one of the first to fully describe the syndrome. 

Sundbeck, G., Lundberg, P-A., Lindstedt, G., Jagenburg, R., and Eden, S., Incidence and prevalence of thyroid disease in elderly women Results from the longitudinal population study of elderly people in Gothenburg, Sweden. Age Ageing 20,291-298 (1991). 

Detectable concentrations of TPOAb are observed in nearly all patients with Hashimoto s thyroiditis and idiopathic myxedema and in the majority of patients with Graves disease. These antibodies have also been demonstrated in the sera of patients with type I insulin-dependent diabetes mellitus. The frequency of detectable TPOAb antibodies observed in nonimmune thyroid disease is similar to that observed in a normal population. ... 

Many specific autoimmune diseases are relatively rare, with an estimated incidence of less than 5 per 100 000 persons per year or an estimated prevalence of less than 20 per 100 000 (Table 7). Other diseases (e.g. rheumatoid arthritis, Graves disease, thyroiditis) are quite common, affecting 1% or more of the population (Cotch et al., 1996 Boberg et al., 1998 Cooper et al., 1998 Marie et al., 1999 Boisseau-Garsaud et al., 2000 Watts et al., 2000 Pillemer et al., 2001 Doran et al., 2002 Kalb et al., 2002 Lovas Husebye, 2002 Feld Heathcote, 2003 Gonzalez-Gay et al., 2003 Mayes et al., 2003 Bogliun Beghi, 2004 Cuadrado et al., 2004). 

Data pertaining to co-morbidity of autoimmune diseases in humans are surprisingly sparse. Few studies are population-based, and few are of sufficient size to address potentially important biological associations, given the relative rarity of many diseases (Scofield, 1996). A recent unpublished review of co-morbidity of rheumatoid arthritis, diabetes mellitus type 1, multiple sclerosis, Crohn disease, and autoimmune thyroid disease found evidence of an increased incidence of autoimmune thyroid disease in patients with rheumatoid arthritis and in autoimmune diabetes (E. Somers, unpublished data). 

Studies of autoantibodies in the general population allow us to determine the prevalence of specific autoantibodies among people who do not have a clinically evident autoimmune disease, whether the prevalence of autoantibodies reflects the demographic variation in disease risk and whether specific environmental exposures are related to the expression of specific autoantibodies. These studies are most feasible for the autoantibodies associated with the most common autoimmune diseases diabetes mellitus type 1, autoimmune thyroid disease, and rheumatoid arthritis. Important issues with respect to interpreting these types of studies include the type of test used and definition of a positive result. 

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