Hi Alain,

You've done a remarkable job of figuring out your labs. Your negative TSI confirms that you're in remission from Graves' disease. The other antibody result is a low level of TPO antibodies. A 1:00 result means that results are positive when 1 ml of your blood is diluted with 99 ml of water. Higher dilutions are negative. In Hashimoto's thyroiditis TPO antibodies are very high, like the results would be positive in a dilution of 50,000. TPO antibodies are considered markers of inflammation and your level would suggest slight inflammation.

About 20% of patients with Graves' disease move into mild hypothyroidism. This hypothyroidism can be transient and it's usually only subclinical or mild.  Subclinical hypothyroidism refers to an elevated TSH and normal levels of thyroid hormone. The hypothyroidism usually occurs when the immune system starts producing blocking rather than stimulating (TSI) TSH receptor antibodies.

Worldwide, all labs use the same units of measurement for TSH. So ideally, we'd all use the same ranges. Many years ago, when we first developed test for TSH we mistakenly used a range of 10-20. The range has been lowered several times since, and since 2003 it's generally been accepted that the TSH range is 0.3-3.0 mu/L, with levels higher than 3.0 suggesting hypothyroidism.

Most laboratories use whatever range their testing kit recommends rather than test the normal population since this is expensive. The idea here is that labs assume that endocrinologists will be familiar with the new guidelines and know what they are. But doctors who aren't familiar with thyroid disease will look at the lab result and assume that a TSH of 5.0 is normal. This is one reason studies show that there's a lot of undiagnosed thyroid disease.

In your case, your TSH suggests subclinical thyroid disease even without relying on the correct range. You could copy several articles I have on TSH and do a google search for TSH reference ranges to learn more about the problem here. You might also want to read some on subclinical hypothyroidism. The chapter in my Graves' book on hypoT will also help.

Subclinical hypothyroidism is usually treated as it can lead to increased lipid levels, depression, joint pain, weight gain and other symptoms. Heart disease is also more common in subclinical hypothyroidism than hyperthyroidism. You might want to read a recent blog I wrote about low FT3 levels in heart disease.

Ideally, your doctor would notice your TSH is high and refer you to an endo.  An endo would test FT3 to see if it's low or on the low side relative to FT4. An endo would also see if you had any risk factors associated with subclinical hypoT and consider prescribing thyroid replacement hormone.

I'm so glad to hear of your sister's remission. Best to you, Elaine