High prevalence of undetected thyroid disorders in an iodine sufficient adult south Indian population.

India is in the transition phase from iodine deficiency to iodine sufficiency, and this is expected to change the thyroid status of the population. The thyroid status and auto-immune status of adult Indian population in the postiodisation phase is largelyunknown, and this study was conducted to answer this question. A cross-sectional population survey was conducted in two phases among the residents of urban coastal area of central Kerala. The initial phase included a house-to-house survey of 3069 adults (>18 years of age), selected by cluster sampling method. From the surveyed population, 986 subjects underwent further physical examination and biochemical evaluation for thyroid function, thyroid autoimmunity status and iodine status. The total prevalence of goitre was 12.2% and median urine iodine excretion was 211.4 mcg/l (mean 220.3 +/- 99.5 mcg/l) indicating iodine sufficiency. Thyroid function abnormalities were present in 19.6% of subjects. Subclinical hypothyroidism was present in 9.4%. Among the population with normal thyroid function, 9.5% and 8.5% respectively had positive anti-TPO and anti-TG antibodies. Among those with thyroid dysfunction, 46.3% had positive anti-TPO and 26.8% were anti-TG positive. A significant proportion of this iodine-sufficient adult population had thyroid disorders. Further studies are required to characterise the reasons for this high prevalence. Iodine deficiency as well as thyroid dysfunction should both be the focus of public health strategies in susceptible populations.