Over or under medicated? Cellular resistance?

[th1ng]

I've recently seen posts here saying blood tests don't mean much if you're medicating with T3/liothyronine at all, even as an addition to T4/levothyroxine, which I'm a little confused about, so I'm wondering if someone can help me understand a bit more:

- I know blood tests can't be 100% relied on, but why is it different when medicating with T3? Surely as long as you're testing FT3 it would still give you the same idea as when medicating with T4?

- I've seen it said 'you might need FT3 over range due to cellular resistance' but wouldn't that also apply if you're medicating with T4?

- how do you actually know if you have a cellular resistance? Isn't it unwise to keep taking more and more medication because you think you're resistant to T3?

- I know some of the symptoms of being undermedicated are the same or similar to those of being overmedicated/hyper - so how do you tell the difference? Eg I've seen some posts from people saying when they reduce their medication they get palpitations; but that can also happen when you initially raise the dose or if the dose it too high, right? If you can't rely on blood tests, how do you know whether you need to raise or lower your dose?

Thanks in advance for any help!

[ShootingStars]

Hi th1ng. That doesn't make logical sense. Maybe who ever says that will chime in and explain what they are thinking? Of course blood tests and current levels are important and will measure your current levels.

1) It's not. Measuring your free levels is measuring your free levels, whether you take only T4, T3 and T4, or only T3. Your levels are whatever what was in your blood the moment your blood was drawn. These levels fluctuate a bit thorough out the day.

2) That is completely inaccurate and can be very dangerous! Neither free should be over range. One should not be super high in the range, and the should not be too low in the range.

2a) I have no idea what that person is talking about; cellular resistance and "needing" to have T3 over range?? Maybe they are talking about something called thyroid hormone resistance, but it is rare. The majority of cases are caused by a gene mutation of the thyroid receptor or by certain medications. Pituitary tumors, other pituitary disorders, nutritional deficiencies, toxins or other health conditions can also influence resistance to thyroid hormones. Thyroid hormone resistance is when there is normal (remember how large the range of normal is) or high TSH accompanied by high FT3 and FT4, and hyposymptoms. The treatment is not to just give more thyroid hormones without risk of some serious implications and symptoms.

2b) T4 should not be taken in high doses that increase levels above 75% of range without risk of additional symptoms, and certainly never to take T4 over range and risk serious implications and symptoms.

3) There is a blood test for resistance to thyroid hormones. It's called RTH test or THRB gene mutation test. Another test is to rule out that a pituitary tumor is not the cause of RTH. This test is called APGH. If levels are similar to those described in 2a but symptoms of hypothyroidism, the cause needs to be determined in case it can easily be corrected, and not just take more thyroid hormones while overlooking the cause.

4) Yes, you can rely on blood tests if you take into account symptoms, and that there are two separate thyroid hormones that both have to be considered. They way that you tell the difference between being under or over medicated is by testing your FT3 and FT4. Too many people are only taking T4 when their bloods show that they need T3 too. Then their FT4 gets too high (leads to symptoms) and their FT3 gets too low (leads to symptoms). Simply lowing T4 dosage would only cause lower T3 and would lead to more symptoms. If one hormone is high and the other is low, then there will be more symptoms over if both hormones were over 50% range, but neither is too high. Yes, too low hormone levels can cause irregular heart rhythm, just as too high levels can.

4a) The way that you know when to increase or decrease your dose is by your FT3 and FT4 levels and corresponding TSH, and by your symptoms.

[Aurealis]

You don’t have to work out if you have resistance, you’ll know if you do because you’ll get problems and feel poorly.

I find that tests are not that helpful but this is a conclusion 20+ years down the line. I cannot tolerate T3 above range but for many years while taking Levo had T4 above range as that was only way I could feel well.

To start off with you have to go by tests and you will learn when to ignore them over time. It can be very difficult to distinguish between too high a dose and too low from symptoms hence tests can be useful.

Because T3 has a short half life test results may be more volatile but the key thing is to standardise when tests are taken eg before medication and breakfast with no T3 in hours before test.

The difficulty is that this group includes many people (like me) for whom hypothyroidism has not responded in the way that most people’s does to treatment. Always assume first that yours is a straightforward case until there is evidence it isn’t.

I have always worked with medics, never gone alone, sorry if this is your situation.

Good luck