Clinical epidemiology of autoimmune thyroid disorders--variation of natural history in patients with autoimmune thyroid disorders

Clinical and epidemiological study for autoimmune thyroid disorders was performed in a rural community. Ninety-six of 1,686 subjects had asymptomatic autoimmune thyroiditis and were followed from 1979 to 1988. TRH loading test was carried out in 91 of 96 cases between 1983 and 1984. Each individual was classified into 4 subgroups. Five patients had normal levels of basal plasma TSH and had no increment of peak levels of plasma TSH (Grade G). Twenty-three had normal levels of both basal and peak plasma TSH (Grade I). The peak plasma TSH levels in 53 patients was high, but the basal was within the normal range (Grade II). Ten had high levels of both basal and peak plasma TSH (Grade III). One of the 5 Grade G cases developed overt Graves' disease in 1987 and another Grade III case suffered from goitrous Hashimoto's thyroiditis with primary hypothyroidism. Four of the ten Grade III cases and one Grade II case developed primary myxedema during the observation period. These results show that the natural history of asymptomatic autoimmune thyroiditis is variable and the prevention of overt autoimmune thyroid disorders is difficult.