Inhibition Iodine

It inhibits oxidation of iodide, inhibits iodination of tyrosine residue and inhibits the coupling of iodotyrosine residue. After oral administration, it is rapidly absorbed and metabolised to methimazole which is active form and crosses the placental barrier. 

Perchlorates, which inhibit iodine uptake by the thyroid gland, reducing T4 and T3 synthesis, constitute another class of environmental chemicals that affect thyroid function. In the past, high doses of these compounds were used to treat hyperthyroidism. In recent years, there has been concern that contamination of drinking-water... 

The effects of amiodarone on thyroid function tests and in causing thyroid disease, both hyperthyroidism and hypothyroidism, have been reviewed in the context of the use of perchlorate, which acts by inhibiting iodine uptake by the thyroid gland (125), and there have been several other reviews (126-130). 

Nitropmsside is given by infusion, and its BP-lowering effect is directly related to the rate at which it is administered. When it is discontinued, the BP rises rapidly. Lethal cyanide poisoning may occur in patients with rhodanase deficiency, and thiocyanate may accumulate in patients with renal failure, thus inhibiting iodine uptake and causing hypothyroidism (see Figure 71). 

The erythrocytes of Co-treated anemic subjects have shorter life-spans. By binding to plasma proteins, cobalt also inhibits iodine transport and is goitrogenic (Herndon etal. 1980). In view of this evidence, the cobalt treatment of anemic subjects has been abandoned, and cobalt-containing anti-anemia iron preparations are no longer marketed in the USA. 

Iodide concentrations higher than normal inhibit iodination of tyrosine, an effect that is useful in the treatment of thyroid disease. Inadequate iodine intake results in diffuse enlargement of the thyroid (goiter). 

Iodine supplementation at iodine deficient baseline inhibited iodine uptake and organization in the thyroid... 

Markou et aL, 2001), and this was the case in about 1% of our patients. Iodine excess inhibits iodine organification and T4andT3 synthesis (WoUf-Chaikoff effect). Normal subjects escape from this effect however, patients with abnormal thyroid gland do not and may develop thyroid hypofunction. Iodine also inhibits thyroid hormone release and decreases serum T4 and T3 levels (Woeber, 1991). Furthermore, iodine seems to be an important factor in thyroid autoimmunity in genetically predisposed individuals (Laurberg... 

Shepherd s purse contains glucosinolates, compounds present in many plants in the Brassicaceae family (e.g., cauliflower and Brussels sprouts). These compounds have been shown to cross the placenta and to be present in breast milk (Panter and James 1990). At high concentrations, glucosinolates inhibit iodine uptake by the thyroid, although at lower concentrations cancer-preventive effects have been shown (Stoewsand 1995). 

At high doses, glucosinolate compounds inhibit iodine uptake although cancer-preventive properties have been shown at lower doses (Stoewsand 1995). 

Long-term administration of sulfonamides at therapeutic dosages can inhibit iodine metabolism, resulting in goiters and thyroid hyperplasia. 

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