Overt thyroid disease

The studied group consisted of 86 university students, 54 females and 32 males aged 18-25 years (mean age 20.7 0.9 years). All of them were without overt thyroid disease their basal TSH levels were within the physiological range. None of the subjects reported having allergic disorders for at least 3 months before the study. There were nine females with basal positive titers of antithyroid autoantibodies (anti-TPO above 25 IU/1 or anti-Tg above 125 IU/1). They were deliberately not excluded from the study in order that the group reflected the middle-European population as much as possible, where up to 10% of subjects display positive titers of antithyroid antibodies. 

Overt thyroid disease is not observed at a rate that differs from controls or the normal population. However, patients receiving therapy should be under the care of a physician who monitors their thyroid status periodically, as subclinical hypothyroidism is a concern. For over three decades the Institute of Medicine (lOM), an operating agency of the Untied States National Academy of... 

Daily I2 treatment of women at doses up to 5 /2 times the UL is not associated with an increase in overt thyroid disease. 

The complexity of the interaction between iodine intake and autoimmune thyroid disease has been highlighted by reports of evidence that iodide (compared with thyroxine) induces thyroid autoimmunity in patients with endemic (iodine deficient) goiter (43), while in those with pre-existing thyroid autoimmunity, evidenced by the presence of antithyroid (thyroid peroxidase) antibodies, administration of iodine in an area of mild iodine deficiency led to subclinical or overt hypothyroidism (44). 

Treatment with levothyroxine is favored in patients with elevated TSH, indicating subclinical or overt hypothyroidism, mostly due to Hashimoto s thyroiditis. In diffuse goiter and nodular thyroid disease, the former practice of sole levothyroxine administration, without additional measures to correct iodine deficiency, has become obsolete, unless the patient lives in an area of ample alimentary iodine supply. 

Teng et al. (2006) explored the effect of iodine intake on thyroid diseases in China. Baseline characteristics of three populations were estabfished in three communities in 1999 and then again 5 years later. The communities had different levels of iodine nutrition mild deficiency more than adequate and excessive intake. Salt iodization had been implemented in China in 1996. In the general population, median UI increased from 165 pg/1 in 1995 to approximately 300 pg/1 in 1999. The concern was with oversupplementation of iodine to a level that is more than adequate, in a region in which iodine intake was previously mildly deficient, which in turn may accelerate the development of subclinical hypothyroidism to overt hypothyroidism. High levels of iodine intake may increase the incidence and prevalence of autoimmune thyroiditis, making it imperative to tailor supplementation needs to each region. 

The laboratory assessment of patients with suspected thyroid disorders must be based on the continuum of disease from subclinical or mild to overt (Fig. 41-2). 

In the adult population, the prevalence of overt hypothyroidism is 19 per 1000 women and 1 per 1000 men with annual incidence of overt hypothyroidism is 4 per 1000 women and 0.6 per 1000 men. Subclinical hypothyroidism is also more common in women, the incidence increases with age, with up to 10% of women older than 60 years having an increased thyroid-stimulating hormone concentration. Subclinical hypothyroidism is more common in people who have been treated for hyperthyroidism with radioactive iodine or surgery, and in those with organ-specific autoimmune diseases, such as pernicious anaemia, type 1 diabetes mellitus, or Addison s disease. 

The therapeutic dosage of iodine is in the range of 100— 200 tg/day. Side-effects of low doses are rare and minor, consisting mainly of iodine-induced acne. Contraindications for the use of iodine are all states of subclinical or overt hyperthyroidism, thyroid autoimmune diseases and the rare dermatological disease Dermatitis herpetiformis Duhring. 

Abbreviations-. oHTA, overt hyperthyroidism in thyroid autonomy scHTA, subclinical hyperthyroidism in thyroid autonomy oHGD, overt hyperthyroidism in Graves disease scGD, subclinical hyperthyroidism in Graves disease MRR, maximum relative risk Inc, incidence RR, relative risk. 

Thyrotoxicosis is a type of very late adverse reaction seen after iodine-based contrast media. Untreated Graves disease and multinodular goiter and thyroid autonomy are risks for this adverse reaction. Patients with hyperthyroidism are usually advised not to have iodinated contrast media injection. Patients with normal thyroid function are thought to be at low risk for this condition [3 ]. There are few studies that assess the relationship between iodinated contrast media exposure and thyroid function disorders. In a nested case-control study of 4096 patient intervals, iodinated contrast exposure was associated with incident hyperthyroidism (odds ratio or OR = 1.98 95% confidence interval or Cl = 1.08-3.60) but not statistically significantly associated with incident hypothyroidism (OR = 1.58 95% Cl, 0.95-2.62). Also, incident overt hyperthyroidism (follow-up thyrotropin levelsO.l mlU/L OR, 2.50 95% Cl, 1.06-5.93) and incident overt hypothyroidism (follow-up thyrotropin level >10 mlU/L OR, 3.05 95% C3,1.07-8.72) were found to be associated with iodinated contrast media exposxue [4 ]. 

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