The SPS - Specialist Pharmacy Service - part of the NHS ediface - recently published this article.
Understanding excipients in medicines
Published 24 June 2024
Topics: Excipients
Guidance on excipients and suggested resources to help find information to support queries about excipients and decision making is provided
sps.nhs.uk/articles/underst...
Nothing particularly surprising, nor specifically relevant to thyroid disorders, but what it says is clearly applicable to all medicines - thyroid hormones as much as any other.
You just might find some of what it says, or links to, is either relevant or provides a useful source to quote when trying to explain any issues you might have.