General Medicine

» Elaine Moore - Hashimoto's Thyroiditis verses Grave’s Disease

In response to Hashimoto's Thyroiditis verses Grave’s Disease posted by Papo1:
Hi,
The first set of labs show subclinical hyperthyroidism although your doctor should have also ordered an FT3 level. If FT4 and FT3 levels are within range and TSH is low this is subclinical hyperT. Subclinical hyperT isn't usually treated since it can resolve as easily as it can worsen, and anti-thyroid drugs could easily make you hypothyroid.

The RAI uptake being normal is expected since your disorder was only subclinical. TSH is a pituitary hormone. When your thyroid hormone levels, FT4 and FT3 begin to rise, the pituitary will stop secreting TSH in an effort to prevent hyperthyroidism (TSH orders your thyroid cells to produce thyroid hormone). TSH levels will fall very low, usually to less than .01 mu/L before your thyroid hormone levels become abnormally high.

The antibody tests confirm that your subclinical hyperthyroidism is autoimmune so you could call it subclinical Graves' disease rather than subclinical hyperthyroidsm.

The confusing part is that long ago labs though that TPO and thyroglobulin antibodies only showed up in Hashimoto's thyroiditis. So some doctors get confused by this. Now, it's well known that up to 90 percent of Grave's patients have these antibodies. And they're markers of thyroid inflammation.

Your actual thyroid status, hyperT or hypoT, tells what your current condition is. And it's not unusual to move between hyperthyroidism and hypothyroidism.

You probably have TSH receptor antibodies, both stimulating and blocking antibodies, that are keeping TSH low.
I'm not sure why you're on methimazole unless there was some new lab report showing a high FT4 or FT3. If you have hyper symptoms but FT4 and FT3 are normal, the usual approach is to use beta blockers to reduce symptoms. These meds also help very slightly to reduce thyroid hormone levels.
Your oddball result is your thyroglobulin level although it's probably false negative with interference from your thyroglobulin antibodies. What's odd is why this test was ordered. It's used to monitor patients who have had their thryoid glands removed to make sure new thyroid cells aren't growing. it's not usually used for diagnosing thyroid disease.
Unless there are some newer results, I'd go with subclinical Graves' disease although with being on meds you could very well have methimazole-induced hypothyroidism for your current status.
Best, Elaine