Thyroid volume

WHO ICCIDD. Recommended normative values for thyroid volume in children aged 6-15 years. Bull World Health Organ 1997 75 95-7. 

Lithium affects thyroid function (52-56), and in most patients, after 4 months of treatment, there is a transient fall in serum levels of thyroxine (T4) and a rise in thyrotropic hormone (thyroid-stimulating hormone, TSH). After 1 year of treatment, these hormones have generally returned to their baseline. The mechanisms for this are obscure, but lithium inhibits both thyroxine synthesis and its release from the gland (201). Lithium may inhibit endocytosis in the thyroid gland, which results in an accumulation of colloid and thyroglobulin within the follicles, thereby reducing hormone release (202). Thyroid volume... 

Langer P, Tajtakova M, Fodor G, et al. 1998. Increased thyroid volume and prevalence of thyroid disorders in an area heavily polluted by polychlorinated biphenyls. Eur J Endocrinol 139 402-409. 

ViTn P, Martino E, Aghini-Lombardi E, et al. (1994) Thyroid volume measurement by ultrasound in children as a tool for the assessment of mild iodine deficiency. J Clin Endocrinol Metab 79 600-603. 

Thyroid volume reflects a populations history of iodine nutrition. 

Thyroid volume, thyroid nodularity, or iodine excretion have close associations to serum Tg, one of the largest iodoglycoproteins in the body with a complex three-dimensional structure, which originates only in the thyroid gland. 

Figure 28.3 Interaction between previous pregnancy, smoking and low iodine intake. The association between tobacco smoking, parity and thyroid volume in the DanThyr population study, inoluding 3712 women. A significant statistical interaction was found for tobaoco smoking on the association between parity and thyroid volume. Reproduced from Knudsen et al., (2002a) with permission.

Note-. 268 school ohildren aged 8-15 years were screened for iodine deficiency in one region of the Czeoh Republic. Actual serum levels of free daidzein, genistein, thyrotropin (TSH), free thyroid hormones, autoantibodies to thyroid peroxidase (AbTPO) and thyroglobulin (AbTg), and ioduria, along with thyroid volume, were measured. S.E.M. shows standard error of the mean. 

Alcohol consumption is associated with a lower prevalence of goiter and thyroid nodules (Knudsen et ai, 2002). The mechanism behind this association remains unclear. Probably, selenium does not significantly influence thyroid volume in at least borderhne iodine-sufficient populations (Brauer et al, 2006b). Moreover, gender, age and parity can play a role in the pathogenesis of goiter (Knudsen et aly 2002), as discussed later in this article. 

Mean thyroid volume was higher in smokers (13.9 ml) than in nonsmoking subjects (12.5ml), without reaching statistical significance (r-test, p = 0.085, 2-tailed). Thyroid volume correlated positively with the reported pack/years of the smokers [Pearson correlation coefficient 0.124 significant at the 0.01 level (2-tailed)]. 

We evaluated whether the parameters age, smoking, gender, pregnancy or nursing period and urinary iodine can predict variable thyroid volume. Linear regression analysis (analysis of variance, ANOVA) revealed a prediction of thyroid volume by age (p < 0.001), gender (j) < 0.001) and smoking (p < 0.05). 

Table 50.2 Distribution of weight, height, surfaoe area and thyroid volume (mean SEM) in the preterm infants studied...

Range of weight (kg) n Postmenstrual age (weeks) Body weight (kg) Body height (cm) Body surface area (m ) Thyroid volume (ml)... 

The most obvious manifestation of iodine deficiency is goiter, an increased thyroid volume. An assumption about goitrogenesis is that, in iodine deficiency, a fall in the blood level of thyroxine (T4) leads to increased thyroid-stimulating hormone (TSH) output from the pituitary. TSH increases the uptake of iodide by the thyroid, with increased turnover of iodine associated with hyperplasia of the follicular cells of the thyroid. The size of the gland... 

Relationship Between Iodine Intake and Mean Thyroid Volume Between Countries/Populations... 

In populations with even mild iodine deficiency, an increased goiter rate can be seen. Delange et al. (1997) have measured thyroid volume and urinary iodine excretion in 5709 children aged 7—15 years in different sites in 12 European countries. All ultrasound examinations and urinary iodine assays were performed by the same investigators. An inverse relationship was found (Figure 55.3). 

A similar study has not been performed in adults. However, one study compared thyroid volume in Sweden and Germany (Gutekunst etal., 1986). Mean thyroid volume was 7.7 4.3 ml in Swedish women and 16.5 12.2ml in Gkrman women. Likewise, mean thyroid volume was 11.1 4.7 ml in Swedish men and 26.9 17.0 ml in German men. Median iodine excretion was 62.6 p,g iodine/g... 

Relationship Between Iodine Intake and Thyroid Volume Within a Population... 

Note-. The table shows correlation coefficients between urinary iodine excretion and thyroid volume in some populations. Most correlations are not significant. Age, gender, and number of subjects in each study are given. Abbreviations-, y, year w, women m, men NS, not significant. 

Relationship Between Various Measures of Iodine Intake and Thyroid Volume... 

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