August 2023 query

Our member asks

Why does TSH sometimes stay persistently low? For example, in someone who has Graves’ disease whose T4 levels are now in range but their TSH remains suppressed?

Our medical advisor replies

This is an unusual phenomenon. The truth is we do not exactly know why the TSH stays chronically suppressed.

I can give you two possibilities:
1. When we measure the thyroid hormones in the blood, it is a snapshot in time. It is not the T3 level throughout the 24 hour period. So, it is possible that in that Graves’ disease patient the snapshot measurement of T3 is ok but over a 24 hour period the thyroid gland is producing just a little too much T3. And this is what accounts for the persistently suppressed TSH.

2. Another explanation, for which there is also good evidence, is that the receptor to which TSH receptor antibodies bind is, strangely enough, also expressed on the TSH producing cells of the pituitary. So, there is a suggestion that the Graves’ antibody cells – the Thyroid Stimulating Hormone Receptor Antibodies (TSHR Ab, also known as TRAb) – is what binds to the pituitary and shuts off the TSH for a long time. I think Prof Moran and I would agree that when we see this in clinical practice we observe this as a
phenomenon that when we treat a patient with Graves’ disease, the TSH can remain suppressed for months. As things get better, it then flips.

July 2023 query

Our member asks

Can the surgical use of iodine cause goitres?

Our medical advisor replies

There is no evidence that iodine uptake scans nor surgical iodine cause nodules or goitres. If anything it is iodine deficiency that causes goitres or nodule, not excess iodine as such. In someone who has Graves’ disease and borderline overactivity, if they took a lot of iodine (i.e. seaweed) this could make their thyroid more overactive in the short term.

Other than that, surgical iodine does not get absorbed into the skin in any meaningful amount. In iodine contrast medium used in x-rays, the amount of iodine is trivial; much, much less than is in a normal diet.

June 2023 query

Our member asks

I have Graves’ disease but no sign of Thyroid Eye Disease (TED). Will having thyroid surgery
reduce the risk of TED developing?

Our medical advisor replies

The Thyroid Stimulating Hormone Receptor Antibodies (TRAb) antibodies which can trigger TED do decline over time when removing the thyroid. We also know that if someone has TED, giving them RAI can make it worse. I am not aware of any concerns about giving RAI for someone with Graves’ disease who hasn’t yet developed TED. Yes, thyroid surgery can be helpful where people already have TED but I wouldn’t be offering surgery to someone just because of worries about developing TED at a later date.

May 2023 query

Would taking levothyroxine increase my chances of a successful pregnancy?

Our member asks

I am struggling to get pregnant after several miscarriages. I have a family history of thyroid problems and have tested positive for thyroid antibodies. Would taking levothyroxine improve my chances of having a successful pregnancy?

Our medical advisor replies

There is no evidence that treating women who have positive TPO antibodies but normal thyroid function tests will result in improved pregnancy outcomes even in those with previous pregnancy losses.

If your TSH is above the pregnancy-specific reference range (or greater than 4.0 mU/L where there are no pregnancy ranges available) then treatment with levothyroxine is recommended.

The evidence for treating those with a TSH between 2.5 mU/L and the upper limit of the pregnancy reference range (or 4.0 mIU/L) who are TPO positive and have recurrent miscarriages is less clear and the TABLET trial showed no benefit. A number of fertility clinics and the current American Thyroid Association (ATA) guidelines however would treat someone with a TSH greater than 2.5 mU/L in this situation.

April 2023 query

Does my son have hypothyroidism?

Our member asks

I believe my son has hypothyroidism as we have a strong family history of thyroid disease. His thyroid function is only showing elevated TSH and a borderline T4. The paediatric endocrinologist has indicated he may develop hypothyroidism in the future but does not currently require treatment. Yet, he is experiencing extreme tiredness, heavy legs, low mood and he has been found to have a low vitamin D. I wish to avoid the problems we had getting his sister’s diagnosis. Is there anything else I should be asking my son’s doctor?

Our medical advisor replies

Firstly, I think it would be good to highlight your concerns with the paediatric endocrinologist.

He or she may make the point that other issues may need to be addressed as well before the picture becomes clear. For example, low vitamin D concentrations can also cause tiredness and heavy legs etc. I imagine your son is on vitamin D now, which may improve his symptoms.

Many studies have shown that subtle TSH increase in isolation (for example, a TSH less than 10mU/l) does not seem to be associated with the kind of profound symptoms that you describe in your son and it would be good to know how high the TSH actually is. If it is persistently elevated in the presence of symptoms, many endocrinologists would consider a trial of thyroxine, particularly if the free T4 is borderline as you suggest. I do think it is important that the team try and understand why the TSH is increased though. Has your son got positive autoantibodies for example? Is he on a diet that does not contain much iodine?

I would just bear in mind that in some individuals mild TSH elevation or mild thyroid dysfunction can actually be the consequence of illness and not the underlying cause. We see this very commonly. If this is the case then the thyroid dysfunction can correct itself spontaneously. Nature and time are sometimes better than a prescription.

Again, this underlines the importance of discussing the specifics with your paediatric endocrinologist who I am sure will be very receptive to your thoughts about the possible way forwards.  

Ultimately, if the TSH continues to rise and the Free T4 continues to fall he will need thyroxine.

March 2023 query

Our member asks:

I was diagnosed with Graves’ disease a few years ago. After taking carbimazole for over a year I became euthyroid and was able to stop treatment. I am now trying to become pregnant and was wondering if I am now completely clear of hyperthyroidism or could the illness come back? 

Our medical advisor replies:

You should have thyroid function tests and thyroid stimulating hormone receptor antibodies (TRAb) checked in the first trimester. Even if you are euthyroid, if the TRAb is positive, you should be referred to a local antenatal clinic during pregnancy. This is precautionary but because thyroid receptor antibodies cross the placenta, monitoring during pregnancy is recommended.

There is a risk of Graves' disease relapse pre-pregnancy or in early pregnancy, or in the postpartum period.Thyroid function tests should be checked if you develop symptoms of hyperthyroidism at any stage, or in early pregnancy. 

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