Does increase in medication affect tsh less the closer you get to optimal level?

[lisan1]

Those of you who are on the right dose of medication or close to it. Has your tsh level decreased less on the same amount of increase in medication the closer you get to optimal tsh levels?

[helvella Administrator]

This isn't a simple issue. For example, with a very high TSH, a modest dose can have a spectacular effect.

Perhaps if you look at the qestion the other way round, it will be clearer?

Assume you are optimally medicated on 100 micrograms and have a TSH of 0.5. Now think what would happen if you reduce the dose by 25 micrograms. Your TSH will rise, possibly by as much as 1.0 - to 1.5. If you increase your dose by 25 micrograms your TSH simply cannot drop by the same amount!

[jimh111]

It's an inverse log linear relationship. If you are old enough to remember slide rules the TSH scale is a bit like a slide rule scale. You would need the same amount of levothyroxine to reduce TSH from 1.0 to 0.5 or from 10 to 5.

[shaws Administrator]

I only have a yearly blood test now but I don't really bother as I now feel well. It's only when you are newly diagnosed, with gradual 25mcg increases until you have no clinical symptoms and feel well that you remain on that dose. If, for any reason, symptoms return, then you get a new blood test. Some doctors make the mistake of thinking that if our TSH gets anywhere in the 'range' i.e. top instead of bottom that they stop increasing. We do need a TSH around 1 or lower and some need it suppressed but doctor will probably argue as they've been told 'suppressed' will give us osteoporosis or harm heart. This isn't true. If we have too much hormone replacements we will feel quite hyperthyroid and realise we have to reduce dose.

Blood tests should be the earliest possible, fasting (you can drink water) and allow about 24 hours gap between last dose of levo and test and take it afterwards. This helps keep the TSH highest and may result in not having your dose adjusted downwards.

TSH means Thyroid stimulating hormone and is from the pituitary gland and it's job is to try to get a thyroid gland to issue more hormones. So the higher it rises the more hypothyroid we are. It reduces as hormone dose is increased and we feel much better with no clinical symptoms.

Also ask doctor to test B12, Vit D, iron, ferritin and folate as we are usually deficient. We need everything to be tip-top.

Always get a print-out of your results each time with the ranges (some surgeries charge a nominal sum for paper/ink) for your own records and you can post if you have a query.

[jimh111]

A picture might be better than complicated words. Have a look at Figure 2 B on this paper journal.frontiersin.org/art... . Notice the how the TSH falls as fT4 increases. Especially notice the TSH scale. You can see that as fT4 (or levothyroxine dose) increases it has progressively less effect on TSH.

By the way this is a great piece of research, but very advanced, so don't expect to understand it.

[Glynisrose]

TSH becomes irrelevent at low numbers.

[lisan1]

Thank you all!