[Effect of mild and moderate excessive iodine supplementation on thyroid function and morphology in non-iodine deficiency rat model].

OBJECTIVE: To study the effect of moderate and mild iodine excess on thyroid function and morphology in non iodine deficiency Wistar rats. METHODS: Serum thyroid-stimulating hormone (TSH) was measured with solid phase radioimmunoassay (IRMA) and serum total T(4) (TT(4)), TT(3), reverse T(3) (rT(3)) and thyroid TT(4) with radioimmunoassay (RIA). Cer-Arsenite colorimetric method was used to measure median urinary iodine (MUI). Thyroid morphological changes were observed under optical and electronic microscope. Metamorphic imaging system was used to measure the height of thyrocytes and the areas of thyroid follicular cavities. RESULTS: Iodine intake of three times than normal for 90 days could increase serum TSH but without significant difference; Serum TT(3) values were markedly lower than those in control, P = 0.0001. Serum and thyroid TT(4) values were markedly higher than those in double distilled water (DDW) group, P value being 0.001 and 0.0001 respectively. However, serum rT(3) did not change markedly when compared with that in DDW group. The area of follicular cavity increased, follicular cells became flat, nucleus stained darker, follicles broke and combined, giant follicles were formed, and the capillaries around the follicules were reduced. The height of thyrocytes was markedly lower than those in DDW group, while the areas of thyroid follicular cavities were markedly larger than those in DDW group (both P values were 0.001). Thyroid ultrastructure showed enlargement of endoplasmic reticulum of thyroid follicular cells, increase of number of secondary lysosomes, darker stain of nuclei, condensation of chromatin and reduction of microvilli. CONCLUSION: Iodine intake over 3 times than normal may potentiate the possibility of hypothyroidism and inhibit the function of most of thyrocytes in non iodine deficiency rats.

[Correlation between serum thyroglobulin and thyroid stimulating hormone in populations with non-toxic goiter].

OBJECTIVE: To investigate the correlation between serum thyroglobulin (Tg) and thyroid stimulating hormone (TSH) in populations with non-toxic goiter. METHODS: Thyroid ultrasonography was conducted, and determination of serum triiodothyronine (FT3), thyroxin (FT4), Tg, thyroid peroxidase antibody (TPOAb), thyroglobulin antibody (TGAb) and TSH, and urine iodine were carried out among 609 persons with an average age of 35.4 in Panshan county, a mild iodine-deficient area in Liaoning province, and 1136 persons aged 39.1 on average in Zhangwu county, an iodine sufficient area in Liaoning province, totally 2 320 persons. RESULTS: The serum TSH levels of the populations with diffuse and nodular goiter in Panshan county were (0.11 +/- 0.08) mU/L and (0.90 +/- 0.10) mU/L, significantly higher than those of the normal population in the same areas (1.33 +/- 0.04) mU/L, both P < 0.01. The serum TSH levels of the populations with diffuse and nodular goiter in Zhangwu county were (1.29 +/- 0.13) mU/L and (0.89 +/- 0.14) mU/L, significantly higher than those of the normal population in the same areas (1.74 +/- 0.04) mU/L, both P < 0.01. The serum TSH level of normal population in iodine deficient area was significantly lower than that of normal population in iodine sufficient area (P < 0.01). The serum TSH level of the normal population in Panshan County was significantly lower than that of the normal population in Zhangwu County (P < 0.01). The serum Tg level of the populations with diffuse and nodular goiter in Panshan county were (12.0 +/- 1.21) ng/L and (50.1 +/- 12.20) ng/L, significantly higher than that of the normal population in the same area (9.1 +/- 2.44) ng/L, P < 0.05 and P < 0.01. The serum Tg level of the populations with diffuse and nodular goiter in Zhangwu county were (12.4 +/- 2.11) ng/L and (61.2 +/- 11.86) ng/L, significantly higher than that of the normal population in the same area (7.7 +/- 2.3) ng/L, P < 0.05 and P < 0.01. The Tg level of the normal population in Panshan County was significantly higher than that of the normal population in Zhangwu county (P < 0.01). The Tg level was positively correlated with the thyroid volume in the nodular goiter population. CONCLUSION: The occurrence of goiter is not directly related to TSH stimulation in mild iodine deficient area. Nontoxic goiter shows a thyroid autonomic function. The major cause of high serum Tg in nodular goiter may be the leakage of Tg into blood circulation caused by degeneration of large colloid follicles and destruction of follicular architecture, not the volume increase of thyroid and its autonomic function.

[An epidemiological study on factors affecting serum thyroglobulin levels].

OBJECTIVE: To investigate the effects of several factors affecting serum thyroglobulin (TG) levels among people aged 14 or more. METHODS: We selected Panshan with median urinary iodine (MUI) 83.45 micro g/L as a deficient iodine intake community, Zhangwu with MUI 242.85 micro g/L as a sufficient iodine intake community and Huanghua with MUI 650.87 micro g/L as an excessive iodine intake community. Serum TG and thyroid stimulating hormone (TSH) were measured in 3,335 subjects whose thyroglobulin antibody (TGAb) were negative and thyroid volume were examined using B-ultrasound. RESULTS: In the population with MUI of 80 - 650 micro g/L, serum TG levels presented a "V" curve. An elevated serum TG was found in both the communities with deficient iodine intake and excessive iodine intake. The same trend was shown in the groups with different levels of serum TSH. An elevated serum TG was found in both the groups of TSH < 0.3 mU/L and TSH > 4.8 mU/L. The serum TG levels was positively correlated with thyroid volume and was higher in female subjects than in male. An increased serum TG was found in subjects of aged 50 in the community with deficient iodine intake. CONCLUSION: Serum TG level is affected by gender, amount of iodine intake, serum TSH level and thyroid volume.