Thyroid volume and nodular and diffuse thyroid diseases by ultrasonography in pregnant women: A case-control study

Iodine status and its association with prevalence of thyroid diseases in adults from Jiangxi Province, China

BACKGROUND

Iodine is an essential element for the biosynthesis of thyroid-stimulating hormone (TSH). Both excessive and deficient iodine are major risk factors for thyroid diseases, including thyroid dysfunction, thyroid nodules, and thyroid autoimmunity (TAI). This study aimed to elucidate the relationship between iodine status and the prevalence of thyroid diseases through a national cross-sectional epidemiological survey in Jiangxi province (China).

METHODS

This population-based, cross-sectional study enrolled 2636 Chinese local inhabitants who aged over 18 years old from April to August in 2015. Physical examination was performed and biochemical indices, urinary iodine concentration (UIC), and TSH level were measured. The Chi-square test, nonparametric test, and 4 multivariate logistic regression models adjusted for risk factors were applied to analysis. Spearman correlation coefficients were calculated to investigate the relationship between iodine intake level and the prevalence of thyroid diseases.

RESULTS

The median UIC was 176.4 μg/L, and a significant difference was found in median UIC between men (182.45 μg/L) and women (169.25 μg/L) (P = 0.03). Among these study subjects, 14.4%, 44.5%, 26.1%, and 15.0% had deficient, adequate, more than adequate, and excessive iodine concentrations, respectively. The prevalence rates of hyperthyroidism, subclinical hyperthyroidism, hypothyroidism, subclinical hypothyroidism, thyroid nodules, and TAI were 0.91%, 0.57%, 0.34% and 7.89%, 9.45%, and 12.7%, respectively. Significant differences were found in iodine status, waist circumstance, systolic blood pressure (SBP), diastolic blood pressure (DBP), total cholesterol (TC), TSH, thyroid nodules, and TAI between men and women (P < 0.05). Compared with those with adequate UIC, subjects with excessive UIC had higher prevalence rates of thyroid dysfunction (odds ratio (OR) = 1.74, 95% confidence interval (CI): 1.40-2.54) and thyroid nodules (OR = 3.33, 95%CI 1.32-8.42). In addition, subjects with deficient and excessive UIC were at the higher risk of TAI compared with those with adequate UIC (OR = 1.68, 95%CI: 1.19-2.60; OR = 1.52, 95%CI: 1.04-2.96, respectively). UIC was positively correlated with the prevalence rates of thyroid nodules (r = -0.44, P < 0.01) and TAI (r = -0.055, P < 0.01). On the contrary, UIC was negatively correlated with the risk of thyroid dysfunction (r = -0.24, P > 0.05).

CONCLUSION

Adult inhabitants from Jiangxi province in the TIDE study were in the adequate iodine status. Excessive iodine status was noted as a risk factor for thyroid dysfunction and thyroid nodules. In addition, both iodine deficiency and excessive iodine were risk factors for TAI.

References values and predictive factors for thyroid volume in pregnant women

Objective

Thyroid volume varies within each population according to different clinical and biochemical factors and can change during pregnancy. The present investigation was aimed to determine the reference values for thyroid volume in pregnant women and their predictive factors.

Materials and methods

A cross-sectional study was carried out with 360 healthy pregnant women. The following variables were examined: maternal age, gestational age, skin color, current smoking status, parity, use of iodinated supplements, body mass index, thyrotropin, total and free thyroid hormones, thyroglobulin, antithyroid antibodies, chorionic gonadotropin, cholesterol and triglycerides.

Results

The mean thyroid volume was 5.3 ± 1.3 mL, 5.4 ± 1.6 mL and 5.6 ± 2.5 mL in the first trimester, second trimester and third trimester, respectively. The reference interval was 2.47-9.49 mL in the first trimester, 3.17-9.01 mL in the second trimester, and 3.00-12.38 mL in the third trimester. Free triiodothyronine and triglycerides were predictors of thyroid volume (corrected R2 = 0.12; p = 0.000).

Conclusion

This study is the first to determine the reference values for thyroid volume and its predictive factors in pregnant women from Cuba, a Caribbean island with sustainable elimination of iodine deficiency disorders.