Answer to Question #9484 Submitted to "Ask the Experts"

Category: Nuclear Medicine Patient Issues — Diagnostic Nuclear Medicine

The following question was answered by an expert in the appropriate field:

I would like to know if having a thyrogen stimulating test using iodine-123 can affect my fertility? I have a strong desire to become pregnant as soon as possible, but I don't know how long I have to wait to conceive or if it will affect my fertility.
The radiation absorbed dose from a thyrogen stimulated iodine-123 uptake is very small and will have no effect on your fertility. 

In the event that the test shows thyroid tissue that needs to be treated with iodine-131, you do not want to be pregnant until all the iodine-131 is out of your body, because it can be taken up by the baby's thyroid and definitely damage it. The amount of time you would have to wait depends upon how much iodine-131 goes to any remaining thyroid tissue, and what your renal clearance time is. On thyrogen for the therapy dose, half of the dose is removed by the kidneys in a typical person every eight hours, but I don't know how fast it will be removed by your kidneys. 

The radiation absorbed dose from iodine-131 is higher than from iodine-123, and it would be advisable to wait at least a month after therapy for theoretical radiation repair of any theoretical radiation damage to the eggs. Your physician should be able to give you a more informed estimate of how long you should wait before conceiving. 

The iodine-131 has not been shown to affect female fertility or cause genetic effects to babies conceived after waiting an appropriate time after the thyroid treatment.

Carol S. Marcus, PhD, MD
Professor of Radiation Oncology and of Radiological Sciences, UCLA
Answer posted on 15 February 2011. The information posted on this web page is intended as general reference information only. Specific facts and circumstances may affect the applicability of concepts, materials, and information described herein. The information provided is not a substitute for professional advice and should not be relied upon in the absence of such professional advice. To the best of our knowledge, answers are correct at the time they are posted. Be advised that over time, requirements could change, new data could be made available, and Internet links could change, affecting the correctness of the answers. Answers are the professional opinions of the expert responding to each question; they do not necessarily represent the position of the Health Physics Society.