A five-year follow-up study of goiter and thyroid nodules in three regions with different iodine intakes in China.
OBJECTIVE
The association between iodine status and the prevalence of goiter and thyroid nodules has been well established but the extent to which different iodine intake levels influence the incidence of goiter and thyroid nodules is unclear. The aim of the study was to determine the incidence of goiter and thyroid nodules in 3 regions with different iodine intake levels: mildly deficient, more than adequate, and excessive.


METHODS
Of the 3385 unselected subjects enrolled in 1999 in Panshan, Zhangwu, and Huanghua where median urinary iodine excretion (UIE) was 83.5 microg/l, 242.9 microg/l, and 650.9 microg/l, respectively, 2708 (80.0%) participated in the follow-up study in 2004. The examinations of thyroid ultrasonography, thyroid function, thyroid autoantibodies and UIE were performed at baseline and follow-up.


RESULTS
The cumulative incidence of diffuse goiter was 7.1%, 4.4%, and 6.9%, respectively, higher in Panshan and Huanghua than in Zhangwu (p=0.013 and p=0.015) and that of nodular goiter was 5.0%, 2.4%, and 0.8%, respectively, declining with increasing iodine intake levels (p<0.001). Mild iodine deficiency, chronic iodine excess as well as positive thyroid autoantibodies were associated with the occurrence of goiter [Logistic regression: odds ratio (OR)=1.83 (95% confidence interval (CI) 1.26-2.65), OR=1.46 (95% CI 1.01-2.11) and OR=1.68 (95% CI 1.14-2.48), respectively]. The cumulative incidence of single nodule was 4.0%, 5.7%, and 5.6%, respectively and that of multiple nodules was 0.4%, 1.2%, and 1.0%, respectively.


CONCLUSIONS
The relationship between iodine and the risk for the occurrence of diffuse goiter shows a U-shaped curve. Nodular goiters are more prevalent in iodine-deficient areas.
Yu
X
X
Institute of Endocrinology, First Hospital Affiliated to China Medical University, Shenyang, Liaoning Province, PR China.
Fan
C
C
Shan
Z
Z
Teng
X
X
Guan
H
H
Li
Y
Y
Teng
D
D
Jin
Y
Y
Chong
W
W
Yang
F
F
Dai
H
H
Yu
Y
Y
Li
J
J
Chen
Y
Y
Zhao
D
D
Shi
X
X
Hu
F
F
Mao
J
J
Gu
X
X
Yang
R
R
Tong
Y
Y
Wang
W
W
Gao
T
T
Li
C
C
Teng
W
W
D000328:Adult; D001323:Autoantibodies / Q000097:blood; D002681:China / Q000453:epidemiology; D004032:Diet; D005260:Female; D005500:Follow-Up Studies; D006042:Goiter / Q000175:diagnosis / Q000453:epidemiology*; D006044:Goiter, Nodular / Q000453:epidemiology; D006801:Humans; D007455:Iodine / Q000008:administration & dosage* / Q000172:deficiency / Q000652:urine; D016015:Logistic Models; D008297:Male; D016017:Odds Ratio; D012727:Sex Characteristics; D013960:Thyroid Function Tests; D013961:Thyroid Gland / Q000000981:diagnostic imaging / Q000276:immunology; D016606:Thyroid Nodule / Q000175:diagnosis / Q000453:epidemiology*; D014463:Ultrasonography
D001323:Autoantibodies; D007455:Iodine