Pregnancy radioactive iodine

Iodides should not be used alone since the normal gland will escape from iodide blockade in 2-8 weeks. Chronic use in pregnancy is not recommended because it crosses placenta and cause fetal goitre. Iodide treatment results in high intrathyroidal iodide content that can delay the onset of thioamide therapy or delay the use for radioactive iodine therapy for weeks if not months. Adverse effects include Hodism which is rare and reversible. The clinical symptoms are acneiform rash, sialadenitis, mucous membrane ulceration, conjuctivitis, rhinor-rhoea, metallic taste and rarely anaphylactoid reaction. 

Radioactive iodine passes the placenta and accumulates in the fetal thyroid where the concentration probably exceeds that in the maternal thyroid. Detailed studies show that the fetal dose of iodine is virtually nil before the 90th day of gestation but sharply increases thereafter (29). This alone is sufficient reason to avoid the use of 131I in pregnancy, but there is also some controversial evidence that various congenital deformities have been produced by the isotope (30). 

Radioactive iodine ( 1) Cure of hyperthyroidism Most cost effective Permanent hypothyroidism almost inevitable Might worsen ophthalmopathy Pregnancy must be deferred for 6-12 months no breast-feeding Small potential risk of exacerbation of hyperthyroidism Best treatment for toxic nodules and toxic multinodular goiter... 

Thyrotoxicosis occurs in about 0.2% of pregnancies and is caused most frequently by Graves disease. Antithyroid drugs are the treatment of choice radioactive iodine is clearly contraindicated. Historically, propylthiouracil has been preferred over methimazole because transplacental passage was thought to be lower however, both propylthiouracil and methimazole cross the placenta equally. Current data suggest that either may be used safely in the... 

Kurtoglu S, Akin MA, Daar G, Akin L, Memur S, Korkmaz L, et al. Congenital hypothyroidism due to maternal radioactive iodine exposure during pregnancy. J Clin Res Pediatr Endocrinol 2012 4(2) lll-3. 

Other treatment options, besides thioamide therapy, involve RAI. The iodine 131 isotope is taken up by the thyroid gland and the radioactivity destroys the gland. RAI is safe, pain free, easy to administer, and very effective. RAI may result in euthyroidism but more frequently results in hypothyroidism requiring lifelong levothyroxine supplementation. RAI should never be given during pregnancy since it crosses the placenta. 

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