Introduction Of Iodine Prophylaxis Research Articles

Changing natural history of differentiated thyroid cancer

The incidence of thyroid cancer has been increasing in many countries over the last 30 years. In the USA, the incidence of thyroid cancer increased from 3.6/100.000 people in 1973 to 8.7/100.000 people in 2002 [1]. This phenomenon is mainly due to an increase in the papillary histotype, which raised from 2.7 to 7.7/100.000, a 2.9-fold increase. The same trend has been reported in Europe [2]. The bulk of the increase is probably the results of better detection of small cancer, measuring 1.5 cm or less. Despite increasing incidence, the mortality from papillary thyroid cancer remained stable (0.5 deaths/100.000 in both 1973 and 2002) [1]. A recent study by Pagano et al. [3] confirm this trend in thyroid cancer patients diagnosed in a tertiary hospital in north Italy, in an area characterized by moderate iodine deficiency. The authors compared the epidemiological and clinico-pathological features of patients according to the time of diagnosis (1997–2005 and 2006–2010). The cut off of 2005 was chosen because it is coincident with the introduction of iodine prophylaxis and with the adoption of international guidelines for the diagnosis and management of thyroid cancer [4, 5]. The main finding is that in more recent years, cancers were diagnosed at an earlier stage, in agreement with the similar observation in other European and North American countries. Increased scrutiny of the thyroid gland, mainly by neck ultrasound, is the most likely explanation for this phenomenon, but the other possibility is that some, as yet unknown, carcinogens in the environment might play a role. Up to now, the only established environmental risk factor for thyroid carcinoma is exposure to ionizing radiation, and the risk, particularly of papillary carcinoma, is greater in subjects of younger age at exposure, as demonstrated following the explosion of the Chernobyl nuclear reactor in 1986 [6]. According to a network of populationbased cancer registries in Italy [7], the temporal trend for thyroid cancer in the period 1988–2002 showed a statistically significant increase of incidence rates in both male and females, that overall showed an annual percent increase of 4.0 % similar to the 3.8 % observed in USA [1]. Based on temporal relationship, it has been claimed that the increase might be a consequence of the Chernobyl fallout. However, no increase in thyroid gland abnormalities, such as nodularity or cancer, was found in northern Italy, among children already born at the time of Chernobyl nuclear accident, when examined 10 years after [8]. This epidemiological evidence does not favor any link between the Chernobyl accident and the increased incidence of thyroid carcinoma in countries other than Belarus, Ukraine, and Russia. Of particular interest is the finding that nearly 20 % of the patients reported by Pagano et al. [3] had an occupational exposure in textile industries. Although the study did not include a control group with the same exposure, the finding recalls a previous Chinese study [9] documenting an association between thyroid cancer and possible exposure to formaldehyde and benzene during long-term employment in textile industries. Another novel finding of Pagano et al. [3] is that cancers diagnosed between 2006 and 2010 presented more frequent association with autoimmune thyroid phenomena. The last observation might be linked to the augmented iodine intake after establishment of iodine prophylaxis in the country and it is in keeping with the evidence that in countries with high nutritional iodine intake the incidence of autoimmune thyroid disorders is higher compared to countries with F. Pacini (&) Section of Endocrinology & Metabolism, Department of Internal Medicine, Endocrinology & Metabolism and Biochemistry, University of Siena, Siena, Italy e-mail: pacini8@unisi.it

A national study of iodine status in Albania

The aim of the study was to determine the iodine status in Albania following 11 yr of iodine prophylaxis and to evaluate factors influencing the outcome. Eight hundred and forty children, aged 6-13 yr, living in 4 different regions and 365 pregnant women living in the same areas, were enrolled for the study. The prevalence of goiter was assessed by palpation and ultrasound imaging and the urinary iodine and the iodine concentration in the salt of different commercial brands were evaluated. Presence of goiter in the family and their eating habits were also investigated as well as the use of iodized salt in the household. In children, the prevalence of goiter was 57.6% by palpation and 24.4% by ultrasound imaging. Median urinary iodine was 86.2 microg/l, with pronounced geographical variations (range 3.52-1079 microg/l). In particular, 29.1% of the children had urinary iodine <50 microg/l and 57.1% <100 microg/l. In pregnant women, the median urinary iodine was 85 microg/l. Median iodine concentration in household iodized salt was 21.2 mg/kg, with 60.3% of the brands being adequately and 39.7% non-adequately iodized. Almost all families (99.6%) claimed to use iodized salt. Despite the introduction of iodine prophylaxis, there is still a mild iodine deficiency in Albania, particularly in the inner mountainous areas.

Tirotoxicosis en una gestación inducida por yodoprofilaxis

We present the case of a 7-week pregnant woman with hyperemesis and liver profile alterations. Viral epatitis and cystic disease were ruled out and an alteration was discovered in thyroid analysis. Subsequent studies ruled out an autoimmune or infectious origin and the patient was diagnosed with thyrotoxicosis induced by iodine-prophylaxis. This phenomenon is known as the Jod-Basedow effect. Treatment with tapering doses of propylthiouracil achieved euthyroid status and improved the patient’s symptoms. The introduction of iodine prophylaxis may increase the incidence of hyperthyroidism.

Autonomy in endemic goiter.

The occurrence of hyperthyroidism in many individuals after introduction of iodine prophylaxis in endemic goiter areas can have dramatic consequences for the affected individuals. It indicates that in such individuals the increase of serum thyroid hormone level in response to iodine supplementation does not exert its normal negative feedback on thyroid activity, ie, that in such individuals some thyroid tissue has become autonomous. In this short review we summarize what is known about the possible mechanisms, cause, diagnosis, and consequences of thyroid autonomy.

Current status of endemic goiter in Croatia: the results of a nationwide study (1995).

In the beginning of the nineties, 40 years after introduction of iodine prophylaxis in Croatia, on a basis of a frequent reports coming from general practitioners about the presence of a rather high prevalence of goiter among schoolchildren, a nationwide study was initiated with the aim to determine the real prevalence of goiter in the country. A total of 2856 schoolchildren of both sexes, aged 7-15 years, were included into the study. Investigations were designed in a way to cover most of geographical regions in Croatia and subjects were randomly selected. The prevalence of goiter in schoolchildren was assessed by palpation and in part by ultrasonography of the neck. At the same time urinary iodine excretion was measured and iodine content in salt samples was determined. The results have revealed the persistence of mild endemic goiter in inland parts of Croatia with the prevalence of 6-29% in the age group 7-11 years and those of 10-43% among the age group 12-15 years. The overall goiter prevalence in schoolchildren in Croatia fluctuates from 8% to 35%. Such prevalence, most probably due to less than optimum iodine intake, is unlikely to change until iodine content of the salt is increased from its present level of 10 mg of Kl per kg of salt.

Importance of cytolytic activity and dietary iodine in the pathogenesis of postpartum thyroiditis.

The incidence of lymphocytic thyroiditis (LT) has increased since the introduction of iodine prophylaxis, and LT is claimed to represent an adverse reaction to iodine. This theory is supported by animal studies as well as experimental studies in humans. In pregnancy iodine turnover is increased. During the immunological rebound period occurring postpartum the thyroid autoantibodies increase, and may lead to postpartum thyroiditis (PPT). The iodine content within the gland may be important for this reaction. In vitro it has been shown that iodine inhibits the cAMP-dependent events of the thyroid cell function, but iodine may also stimulate the intrathyroidal immuno-competent cells leading to cytokine synthesis. Cytokines have been shown to interfer with the thyroid cell function. Iodine may thus trigger the autoreactive attack and enhance the local autoantibody production, which plays a primary pathogenic role for development of PPT.

Thyroid volume of East Slovakian adolescents determined by ultrasound 40 years after the introduction of iodized salt.

Thyroid volume was examined by ultrasonography in 207 boys and 220 girls aged 15-16 years from East Slovakia and it was found that 49.3% of the boys and 52.3% of the girls had thyroids between 10 and 15 ml. These thyroid volumes resemble those found in school children from areas of mild iodine deficiency (e.g. FRG) and are twice as large as those reported from Sweden, where iodine intake is sufficient. The findings were compared to these reported by others in 1949-53 before the introduction of iodine prophylaxis. It may be concluded that 40 years of goiter prophylaxis with iodized salt, though resulting in urinary excretion of approximately 100 micrograms/24 hr (as found by others in 1984), abolished large and medium size goiters in adolescents and decreased a prevalence of goiter grade I to about 25 percent, but appeared still to be insufficient to prevent goiter grade I completely.