Papillary:follicular carcinoma ratio

Table 53.5 Papillary follicular carcinoma ratio in nonendemic goiter regions with or without iodination policy...

A rise in papillary carcinoma from most series is accompanied by a decrease in the incidence of follicular carcinoma, which was sometimes not as marked as in Salta (Tables 53.4 and 53.6), probably due to the use of routine systematic capsule sampling from follicular neoplasms from the 1980s leading to more frequent identification of minimally invasive follicular carcinomas (Harach et al, 2002 Harach and Williams, 1995 Lang et al, 1980). If this had occurred, the real change in the papillary to follicular carcinoma ratio would have been greater, but would not have affected the incidence of papillary carcinomas, as microcarcinomas were excluded. Furthermore, an increase... 

The beneficial effects of iodine supplementation in the prevention and control of developed thyroid abnormalities due to iodine deficiency have been discussed so far in this chapter. However, supplementation with excess iodine, including the improvement of a previous iodine-deficient state, may cause thyroid dysfunctions, viz., iodine-induced hypothyroidism/iodide goiter in susceptible subjects (Roti and Vagenakis, 2000) and iodine-induced hyperthyroidism (IIH) especially in individuals over 40 years of age and who have been iodine deficient for a long period in the past (Vidor et ai, 1973). It may also increase the ratio of papillary/follicular carcinomas (Slowinska-Klencka et ai, 2002). In other words, both low and excess intake of iodine is related to further risk of thyroid disease. Although a daily intake of up to 1000 pg/day by a normal adult individual is quite safe (WHO, 1994), the upper limit is much lower in a population that has been exposed to iodine deficiency in the past. Therefore, to prevent IDD, the recommended iodine requirement in an adult individual is fixed within a narrow range of 150 rg/day (Knudsen et ai, 2000). Iodine supplementation under certain conditions in certain populations causes adverse effects, e.g., iodide goiter and iodine-induced hypothyroidism, IIH, iodine-induced thyroiditis and thyroid cancer. 

The ratio of papillary to follicular carcinoma increases after iodine prophylaxis. 

CLINICAL SIGNIFICANCE - There are no young cretinoids and more subtle effects of iodine defficiency in children were not studied. However, hyperthyroid patients from the most affected areas presented with a high prevalence of nodular lodbasedow, as compared to Graves disease. Also, the ratio of follicular to papillary carcinomas was different in affected and non affected regions. As these data were obtained from an hospital based registry only ratios could be calculated but not absolute incidences or prevalences. 

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