T3, T4, TSH and Thyroid Cancer: What you REALLY need to know

by thycarant

Let me preface this post by clearly stating, I am not a medical doctor.  I am simply a thyroid cancer survivor, well-read and well-informed.  Always consult your physician about any medical information you have come across.

I’m going to try to keep this info simple.  If you have any questions about what I have posted, please, leave a comment.  I will try to address it.

What the thyroid does: it produces the hormones T3 & T4.

What happens when you remove the thryoid: you need to replace the T4 hormone.

Why not replace the T3 hormone: your body will convert T4 to T3.

What is TSH: Thyroid Stimulating Hormone.

Why is TSH important: in papillary and follicular thyroid cancers, TSH suppression (below 0.5 for the first few years, at least) is an integral part of preventing thyroid cancer recurrence.

I keep reading that I should only focus on the T3 and T4 levels to decide if I am hypo or hyper thyroid: that is incorrect.  You no longer have a thyroid, you are fully dependent on an oral T4 pill.  If you do not take your T4 pill your body has no way to produce T4 (or T3).  You do not have a thyroid, so you do not have a malfunctioning thyroid.  You are not hyper or hypo thyroid if you are taking your pill, daily.  You should ALWAYS focus on your TSH, that is the integral part of your thyroid cancer management, for the rest of your life.

But I have symptoms: your dose can be too high or too low and there are symptoms that go along with that.

But everything online says I will only feel good if I take a T3 or take a ‘natural’ thyroid pill with both T3 & T4: if you truly are not feeling good, ask your doctor to try a different brand or type of thyroid med. ‘Natural’ thyroid is derived from pig. It contains T4 and T3, but the ratios are not same as the human thyroid produces. Some swear by it. The  vast MAJORITY of thyroid cancer patients feel perfectly fine on synthetic T4 (levothyroxine sodium) and before buying the online bullshit about needing T3, try the T4 for yourself and give it time (at least a year).

But I keep reading that my T3 & T4 levels need to be in the ‘upper range’ and if they’re not, I’m going to be hypo, even if my TSH is 0.0001: first, that’s a pile of rubbish based on zero medical studies.  Second, these ranges for T3 & T4 are used IN CONJUNCTION with TSH to diagnosis hyperthyroid or hypothyroid: both diseases of the thyroid (which you no longer have). You do not have a malfunctioning thyroid, T3 & T4 measures are going to tell you very, very little.

But there are people online, authors, etc. who INSIST that T4 only is not good enough.  There is one website telling me I need to stop the madness: these ‘authors’ are targeting people who think they have hyperthyroid or hypothyroid, not people with thyroid cancer.  As far as I can tell, these ‘authors’ don’t know shit about managing thyroid cancer and want to lump symptoms of a dose too high or too low into hyper or hypo thyroid.  It Is Not The Same.

Maybe I’m a ‘poor converter’:  yes, I have read about the ‘poor converter’ of T4 to T3 in many online forums.  But where I have not read about this condition is in medical studies.  It’s not real.  Hey, if you feel better taking a T3, then more power to you, but being a ‘poor converter’ of T4 to T3 is not medically real.  It’s not, at least from what I’ve read.  If you know of studies supporting ‘poor T4 to T3 conversion’, please feel free to share it.

I hear I need to eat more selenium to make sure I am converting T4 to T3:  selenium deficiency in the US (and developed nations) is RARE!

“Human selenium deficiency is rare in the United States but is seen in other countries, most notably China, where soil concentration of selenium is low”


The bottom line:  monitor your TSH.  if you have symptoms of a dose too high (ex: anxiety, fatigue, insomnia) or a dose too low (ex: fatigue, depression, impaired memory) contact your doctor.  TRUST your doctor when (s)he tells you that Free T3 is meaningless to thyroid cancer management (you do not have a malfunctioning thyroid).  Your TSH  HAS to be at or below 0.5 (at least for the first few years) and within that range, there should be a perfectly comfortable TSH level where you can reside.

If you really can not tolerate a TSH level below 0.5, you’ll need to ask yourself what is more important in life.  Maybe you’ll need to let your TSH rise to 1.00 to feel right.  Work with your doctor and ask your doctor about the disease of hyperthyroid, the disease of hypothyroid, and if you could possibly have either without a thyroid.