Thyroid UK
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At last an Endo who listened to me & is testing T3

Saw endo today, having been hypo for 15 years, now suddenly TSH dropped to 0.05 and have had my meds dropped from 100mg to 75mg. He listened to all my symptoms which are still hypo and has done a blood test for T3 levels and said if low he will treat and review the symptoms. Fingers crossed I get somewhere, any one else been through this process?

9 Replies

What was your FT4? He should not be dropping your dose simply on the grounds of a low TSH. Once you are on thyroid hormone replacement, the TSH is irrelevant. 75 mcg is a very low dose, so you'll probably end up with even more symptoms.


It was gp that reduced the dose, hence my request to see an endo.


Well, you should still have put up a fight! lol I hope the endo is more clued up.


I had no idea that once on thyroid hormone replacement, the TSH is irrelevant. Grateful for explanation please.


TSH = Thyroid Stimulating Hormone. It's secreted by the pituitary, when the pituitary senses that there's not enough thyroid hormone in the blood. It's a feed-back loop. When the pituitary senses that there is enough thyroid hormone in the blood, it stops secreting so much TSH, just enough to keep the thyroid ticking over.

However, if your thyroid is sick for any reason, and can't produce more hormone, the TSH builds up in the blood. And, that's why you have high TSH when you have primary hypo, and the Frees are low in range because the gland isn't responding.

The gland can't respond, so you take thyroid hormone replacement. And now, the feed-back loop is interrupted, and is no-longer reliable. It is capable of dropping very low when you start taking levo, even though you aren't on enough to make you well.

And, if you can't can't convert the T4 you're taking, the FT4 will become high, and the TSH low, but you will still be hypo, because your FT3 is still low. And, it's low T3 that causes symptoms, nothing to do with the TSH. But, the TSH won't always tell you that you can't convert, and the FT3 is low.

So, then you may start taking T3. And, the pituitary senses T3 in the blood, and suppresses the TSH. And this can happen on quite a low dose of T3, because when the T3 is shared out, so to speak, the pituitary is served first. So, the pituitary has enough T3, but that doesn't mean that the rest of the body does. And, the reason it suppresses the TSH is because it is no-longer needed. If you have sufficient T3, there is no need to stimulate the thyroid. It doesn't mean that you are over-medicated - sometimes you can be under-medicated. It just means that you just don't need it.

TSH also drops throughout the day, being higher early in the morning, but doctors don't take account of this and are capable of taking blood tests at 7 in the evening, when the TSH will be very low.

TSH also drops after eating. And, it can rise if you are ill. It can be suppressed even when your Frees are still quite low. And, in general, can be affected by so many things, that it really is not a very reliable test, rarely reflects thyroid status and/or your well-being, and therefore should not be used for the purpose of dosing the patient.


thank you greygoose x


You're welcome. :)


really pleased fo r you shelly and I hope yu get the help you need.

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One thing the consultant did, never had done before, is the Achilles reflex test, I felt it but don't think my foot moved?


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