From the Guidelines
The optimal time to conceive after radioactive iodine therapy for hyperthyroidism is at least 6-12 months after treatment, however the provided evidence does not specify this time frame.
Important Considerations
- Radiation Safety: The evidence from 1 suggests that radiation therapy, such as I-131, should not be administered during pregnancy, implying that conception should be delayed until after the radioactive iodine has been cleared from the body.
- Breastfeeding Precautions: According to 1, women should not breastfeed for four months after I-131 treatment, which further supports the idea of delaying conception.
- General Guidelines: Although the exact timing is not specified in the provided evidence, general guidelines in clinical practice often recommend waiting at least 6-12 months after radioactive iodine therapy before attempting to conceive, to minimize potential risks to the fetus.
- Individualized Approach: The decision on when to conceive after radioactive iodine therapy should be made on a case-by-case basis, taking into account the individual's overall health, the severity of their hyperthyroidism, and the specific treatment they received.
From the Research
Optimal Time to Conceive after Radioactive Iodine Therapy
The optimal time to conceive after radioactive iodine therapy for hyperthyroidism is a topic of interest due to the potential risks associated with radiation exposure.
- Studies have shown that radioactive iodine administration during pregnancy can cause severe and potentially irreversible hypothyroidism in neonates, with consequent mental retardation, and it is contraindicated during the whole pregnancy 2.
- However, a case report suggests that when radioactive iodine administration happens around the third week of gestation, pregnancy outcome can be normal 2.
- Most guidelines recommend avoiding pregnancy for four to six or even 12 months after RAI treatment or scanning 3.
- The effect of radioactive iodine treatment is complete in 4 to 6 months, and patients with hyperthyroid disease who are unimproved at 3 months can be retreated with RAI without further delay 4.
- Women requiring thyroid hormone replacement after definitive therapy for Graves' disease who later conceive require an early increase in levothyroxine dose and monitoring of thyroid hormone levels throughout pregnancy 5.
- Cure rates after RAI therapy range between 80% and 100%, with some patients requiring two or more doses, and the overall cure rate was 87.7% amongst patients who received a single dose of RAI therapy 6.
Considerations for Conception
- The washout of 131I from the whole body takes place in a few days, but the risk of mutagenic effect on germ cells is a concern 3.
- Measurement of TSH receptor antibodies (TRAb) during pregnancy is recommended, as they can cross the placenta and affect the fetus 5.
- Adherence to the current American Thyroid Association guidelines is poor, and further education of both patients and clinicians is important to ensure that treatment of women during pregnancy after definitive treatment follows the currently available guidelines 5.