Dr. WEEKS’ COMMENT:
“Japanese population that consumes 25 times the median intake of iodine consumption in the United States. Japan’s population suffers no demonstrable increased incidence of autoimmune thyroiditis or hypothyroidism.“
Cancer Causes Control. 2009 Feb;20(1):75-86. Epub 2008 Sep 3.
Risk factors for thyroid cancer: an epidemiological review focused on nutritional factors.
Unità di Epidemiologia e Biostatistica, Centro di Riferimento Oncologico, Via F. Gallini 2, Aviano (PN), 33081, Italy. firstname.lastname@example.org
OBJECTIVES: The present review summarizes epidemiological evidence on risk factors for thyroid cancer (TC), in particular, nutritional factors. METHODS: Searches of articles on the issue were conducted using MEDLINE. RESULTS: Exposure to ionizing radiation, particularly during childhood, is the best-established risk factor for TC. There is also a strong association with history of benign nodules/adenoma or goiter. Iodine deficiency may induce an increasing incidence of benign thyroid conditions, but very high iodine intake also affects thyroid function and, possibly, TC risk. Among dietary factors, fish-the major natural source of iodine in human diet-is not consistently related to TC risk. High intake of cruciferous vegetables shows a weak inverse association with TC. Among other food groups, vegetables other than cruciferous are the only food group showing a favorable effect on TC, with an approximate 20% reduction in risk for subjects with the highest consumption. No effect on TC risk of alcohol, coffee, or other food-groups/nutrients emerged. Height and weight at diagnosis show a moderate positive association with TC risk.
- CONCLUSION: At present, the only recognized measures for reducing TC risk is to avoid ionizing radiation and iodine deficiency, particularly in childhood and young women, and to increase vegetable consumption.
2: Endocr Pathol. 2008 Winter;19(4):209-20.
Thyroid cancer, thyroiditis and dietary iodine: a review based on the Salta, Argentina model.
Servicio de Patología, Hospital “Dr. A. Oñativia”, E. Paz Chain 36, 4400 Salta, Argentina. email@example.com
Factors that should be considered when studying the effect of dietary iodine in the development of thyroid cancer include pathological criteria, diagnostic techniques, screening programs, radioactive fallout, and standard of medical care in the studied population. In most surveys, papillary carcinoma forms the largest group of thyroid malignancies, both before and after iodine prophylaxis where an increase in the papillary:follicular carcinoma ratio is also noted. Undifferentiated carcinomas decrease after salt prophylaxis. In Salta, Argentina, the increasing incidence of clinically significant papillary thyroid cancer and the decrease of undifferentiated carcinoma after iodine prophylaxis are probably due to better access to health centers and consequent earlier detection of differentiated precursor tumors. Autoimmune focal and diffuse or Hashimoto’s thyroiditis are linked to dietary iodine. Pathological studies made in different regions indicate that these types of thyroiditis occur more frequently in areas of iodine sufficiency than in areas of iodine deficiency, and increase after iodine prophylaxis both in non-goitrous and iodine-deficient areas like Salta, Argentina. An increase of lymphocytic thyroiditis could be linked to an increased incidence of primary thyroid lymphoma, and thyroiditis is more commonly associated with papillary carcinoma than with other types of thyroid follicular or C-cell derived carcinomas regardless of iodine intake.
3: Altern Med Rev. 2008 Jun;13(2):116-27.
Iodine: deficiency and therapeutic considerations.
Southwest College of Naturopathic Medicine, USA. firstname.lastname@example.org
Iodine deficiency is generally recognized as the most commonly preventable cause of mental retardation and the most common cause of endocrinopathy (goiter and primary hypothyroidism). Iodine deficiency becomes particularly critical in pregnancy due to the consequences for neurological damage during fetal development as well as during lactation. The safety of therapeutic doses of iodine above the established safe upper limit of 1 mg is evident in the lack of toxicity in the Japanese population that consumes 25 times the median intake of iodine consumption in the United States. Japan’s population suffers no demonstrable increased incidence of autoimmune thyroiditis or hypothyroidism. Studies using 3.0- to 6.0-mg doses to effectively treat fibrocystic breast disease may reveal an important role for iodine in maintaining normal breast tissue architecture and function. Iodine may also have important antioxidant functions in breast tissue and other tissues that concentrate iodine via the sodium iodide symporter.
4: J Endocrinol Invest. 2008 Mar;31(3):243-50.
A five-year follow-up study of goiter and thyroid nodules in three regions with different iodine intakes in China.
Institute of Endocrinology, First Hospital Affiliated to China Medical University, Shenyang, Liaoning Province, PR China.
OBJECTIVE: The association between iodine status and the prevalence of goiter and thyroid nodules has been well established but the extent to which different iodine intake levels influence the incidence of goiter and thyroid nodules is unclear. The aim of the study was to determine the incidence of goiter and thyroid nodules in 3 regions with different iodine intake levels: mildly deficient, more than adequate, and excessive. DESIGN, PATIENTS AND MEASUREMENTS: Of the 3385 unselected subjects enrolled in 1999 in Panshan, Zhangwu, and Huanghua where median urinary iodine excretion (UIE) was 83.5 microg/l, 242.9 microg/l, and 650.9 microg/l, respectively, 2708 (80.0%) participated in the follow-up study in 2004. The examinations of thyroid ultrasonography, thyroid function, thyroid autoantibodies and UIE were performed at baseline and follow-up.
- RESULTS: The cumulative incidence of diffuse goiter was 7.1%, 4.4%, and 6.9%, respectively, higher in Panshan and Huanghua than in Zhangwu (p=0.013 and p=0.015) and that of nodular goiter was 5.0%, 2.4%, and 0.8%, respectively, declining with increasing iodine intake levels (p<0.001). Mild iodine deficiency, chronic iodine excess as well as positive thyroid autoantibodies were associated with the occurrence of goiter [Logistic regression: odds ratio (OR)=1.83 (95% confidence interval (CI) 1.26-2.65), OR=1.46 (95% CI 1.01-2.11) and OR=1.68 (95% CI 1.14-2.48), respectively]. The cumulative incidence of single nodule was 4.0%, 5.7%, and 5.6%, respectively and that of multiple nodules was 0.4%, 1.2%, and 1.0%, respectively.
- CONCLUSIONS: The relationship between iodine and the risk for the occurrence of diffuse goiter shows a U-shaped curve. Nodular goiters are more prevalent in iodine-deficient areas.
PMID: 18401207 [PubMed – indexed for MEDLINE]
6: J Clin Apher. 2008;23(2):92-5.
Refractory thyrotoxicosis induced by iodinated contrast agents treated with therapeutic plasma exchange. A case report.
Service of Endocrinology, Regina Elena Cancer Institute, Rome, Italy.
Excess free iodide in the blood (ingested or injected) may cause thyrotoxicosis in patients at risk. Iodinated contrast solutions contain small amounts of free iodide and may be of significance for patients affected by Graves’ disease, multinodular goiter or living in areas of iodine deficiency. Herein, we report a 57 elderly woman with a clinical history of multinodular goiter presented with a thyrotoxicosis induced by an iodinate contrast agent used during computed tomography scan. Because of the patient’s resistance to conventional antithyroid drugs, she was treated with therapeutic plasma exchange (TPE). TPE is used in the treatment of several immunologic and nonimmunologic disorders. Temporary improvement after TPE in cases with thyrotoxicosis has been reported. In our patient’s case, we observed an improvement in the thyroid hormone laboratory values as well as clinical findings. TPE can be an addition treatment when standard therapies for thyrotoxicosis fail providing the clinician with an adjuvant tool for rapid preparation of such a patient for thyroidectomy surgery. (c) 2008 Wiley-Liss, Inc.