Technetium-99m Pertechnetate Thyroid Scan and Breastfeeding
Technetium-99m pertechnetate thyroid scanning is NOT safe during active breastfeeding and requires interruption of nursing for hours to days after the procedure.
Key Recommendation
The 2018 ACC/HRS/NASCI/SCAI/SCCT Expert Consensus Document explicitly states that for Tc-99m pertechnetate, interruption in breastfeeding is recommended, for hours to days 1. This is the most authoritative and recent guideline addressing this specific question.
The FDA drug label for Tc-99m pertechnetate confirms that "Sodium Pertechnetate Tc 99m is excreted in human milk during lactation; therefore formula feedings should be substituted for breast feeding" 2. The label further states this preparation "should not be administered to pregnant or lactating women unless expected benefits to be gained outweigh the potential risks" 2.
Clinical Context and Alternatives
When Radioiodine Scans Are Contraindicated
The 2011 American Thyroid Association guidelines note that when radioactive iodine is contraindicated, such as during pregnancy or breastfeeding, ultrasound with increased color Doppler flow may be helpful in confirming thyroid hyperactivity 3. This provides a radiation-free alternative for evaluating thyroid function in nursing mothers.
Radiation Exposure Considerations
While a single Tc-99m pertechnetate scan delivers relatively low radiation (the European Heart Journal notes nursing mothers should not breastfeed for 15 hours after the scan as significant quantities of Tc-99m are secreted in milk 4), the radiotracer is actively concentrated in breast tissue through the sodium/iodide symporter (NIS), which is greatly enhanced during lactation 5.
Practical Management Algorithm
If the scan is clinically essential:
- Perform the scan
- Interrupt breastfeeding for at least 15-24 hours (based on the physical half-life of Tc-99m being 6 hours)
- Pump and discard breast milk during this period
- Resume breastfeeding after the interruption period
If the scan can be deferred:
- Consider ultrasound with Doppler flow as first-line imaging
- Postpone nuclear imaging until after weaning
- Use clinical and biochemical parameters (TSH, free T4, TRAb) for diagnosis
Important Caveats
The exact duration of breastfeeding interruption varies in the literature from "hours to days" 1. A conservative approach of 24 hours is reasonable given Tc-99m's 6-hour physical half-life, allowing for approximately 4 half-lives of decay. Some sources suggest 15 hours may be sufficient 4, but individual institutional protocols should guide the specific duration.
The decision to proceed must weigh the clinical urgency of thyroid evaluation against the disruption to breastfeeding and potential infant exposure to radioactivity through breast milk.