This will be done either by using Thyrogen (Recombinant Human TSH)or stopping your thyroxine treatment (often referred to as ‘thyroxine withdrawal’).
Most centres use Thyrogen for this test as recommended in the latest BTA guidelines.
Some centres will do scans and blood tests, others will do blood tests only.
In order to prepare for the blood test/ scan you will be asked to:
- Commence on low iodine diet for three weeks
- You will also have blood taken to test thyroglobulin levels. You will be given Thyrogen (Recombinant Human TSH). If so, you will not need to stop thyroxine but will need to come to the hospital each day for a week as follows:
- Day 1 Thyrogen injection (10 minutes)
- Day 2 Thyrogen injection (10 minutes)
- Day 5 Blood test for thyroglobulin (in some cases a scan will also be done on Day 4 after a small dose of RAI on Day 3)
- Switch from T4 to T3 for two weeks
- Stop T3 for two weeks
- If you are having a scan in addition to blood tests you will be asked to attend the Nuclear Medicine Department as an outpatient for:
- Day 1: Low dose RAI capsule (10 minutes) usually done on a Wednesday
- Day 2: Neck scan (approx eight minutes) on Thursday
- Day 3: Body scan (approx 40 minutes) on Friday
In centres who do not use Thyrogen you will be asked to