ABSTRACT
Objective To investigate the prevalence of common thyroid diseases and urinary iodine levels in the population migrated from inland to coastal areas and to evaluate the epidemiological trend of thyroid disease in Heibei Cangzhou. Methods A retrospective analysis method was adopted. All the persons who were employees of enterprises and institutions,were divided into three groups:the migrated group,who migrated from Cangzhou City and the west counties of Cangzhou City to the Port of Huanghua where they had settled permanently because of the job; the inland group, who lived in Cangzhou City all the time and the seaport group, who lived in the Port of Huanghua for a long-term. Migrated groups were divided into stable occupants and intermittent occupants. During 2010 - 2016, a follow-up survey was conducted in the three groups at Examination Center of Cangzhou Central Hospital Physical. We compared the cumulative incidences of thyroid diseases including: chronic lymphocytic thyroiditis (CLT), nodular thyroid disease and Graves's disease (GD). In migrated group, 28 persons who occasionally lived in the Port of Huanghua were detected urinary iodine levels intermittently.We compared the two parts of urinary iodine level changes for three times by collecting a urine sample,including one part from people who lived in the Port of Huanghua continuously for more than a month,and another part of people who lived in Cangzhou or Hejian County for more than half a month then returned to Port of Huanghua. Results In 2010 - 2016, a total of 7 180 residents were surveyed, of which 2 012 were in the migrated group, 2 858 were in the inland group and 2 310 in the seaport group. The incidences of CLT and nodular thyroid disease were 2.29% (46/2 012)and 8.60% (173/2 012)in the migrated group,which were much higher than that of the inland group and the seaport group [1.05% (30/2 858), 5.42% (155/2 858); 1.47% (34/2 310), 6.88% (159/2 310), P < 0.01 or < 0.05]. At the same time,the incidences of GD was 0.45%(9/2 012) in the migrated group, which was higher than that of the inland group [0.10% (3/2 858), P < 0.05]. In migrated group, there were 1 503 residencies, including 482 stable occupants and 1 021 intermittent residents. The incidences of CLT and nodular thyroid disease in intermittent residents were 3.23% (33/1 021) and 9.89% (101/1 021), which were much higher than that of stable occupants [1.45% (7/482), 6.64% (32/482), P < 0.05]. The urinary iodine levels in the persons who lived in the Port of Huanghua occasionally (464.6 μg/L) were much higher than that of the persons who lived in Cangzhou for a long time(301.4 μg/L, U = 4.648, P < 0.01).There was a marked fluctuation of the median of urinary iodine determined 6 times which were 485.7,285.2,431.7,310.6,470.3 and 304.4 μg/L,respectively.Conclusions The incidence of many thyroid diseases of people migrated from inland to coastal areas has increased, which is not only higher than that of inland people,but also higher than that of coastal people.Large fluctuations in iodine intake due to migration flow and residential instability may be part of the reason for the high incidence of thyroid diseases. In the future, we should pay more attention to thyroid diseases of migratory population.