**Acknowledgements**

may be associated with attention deficit disorders and impairment of figurative memory in the offspring and also a slightly increased cancer-risk possibility. According on the gestation

• Early fetal stage (8th–15th week): neurological alterations such as decrease of the intellec-

• Late fetal stage (15th–25th week): neurological alterations and risk of developing radio-

• Special mention with the use of 131I, therapeutic administration of radioiodine to the mother after the fetal gland is formed (after about 10 weeks into gestation) can result in fetal hypothyroidism. This is because after the eleventh week, the fetal thyroid concentrates iodine,

For these reasons, radioiodine therapy is contraindicated in pregnancy, being the pharmacological treatment with oral antithyroid drugs the first line of therapy, mainly with propylthiouracil. Radioiodine would be acceptable when pregnancy is contemplated after at least 6 months, and thyroidectomy if conception is envisaged within a 6 month interval and/or if there is a large goiter [3]. It must also be borne in mind that these possibilities of therapy are considered second line, in the case of contraindication, refractoriness or failure to adherence

Regarding breastfeeding, there are general guidelines on the time of interruption depending on the radiopharmaceutical used. In the case of <sup>131</sup>I for therapeutic purposes, breastfeeding should be completely suppressed after administration of 131I. This condition does not occur with antithyroid drugs, since studies have shown that only limited amounts of propylthiouracil or carbimazole are secreted in breast milk, which explains that the neonatal exposure to these drugs is insignificant. Therefore, the use of low-moderate doses of carbimazole (<20 mg)

Patients with chronic renal failure do not have a contraindication to receive treatment with

Holst et al. reviewed the medical literature and concluded that the 131I dose does not need to be adjusted in patients who have end-stage renal disease and who are referred for the therapy of hyperthyroidism. However, they recommended 131I administration as soon as possible after dialysis and a delay in subsequent dialysis until the maximum 131I uptake has occurred in the

Some cases of contamination of dialysis machines have been reported. In these cases where there may be a slight contamination with 131-Iodine in disposable items such as syringes or waste bags, these can be stored for several half-life periods until activity declines. Also these

or propylthiouracil (<300 mg) during breastfeeding is recommended [3].

period the patient is in, there is a greater probability of risk of [3, 16]:

induced cancer that will be suffered before the age of 15 years.

and if the fetus is exposed, it will be born athyrotic.

to pharmacological therapy with anti-thyroid drugs.

**8.2. Chronic renal failure and dialysis**

131-Iodine.

thyroid [16].

tual coefficient.

44 Thyroid Disorders

• Pre-implantation stage (second week): abortions *("all-or-nothing law")*.

• Stage of organogenesis (second–eighth week): congenital malformations.

All authors have read and approved the manuscript and affirm that the requirements for authorship have been met:

