Does your body stop converting T4 to T3 when you take Cytomel?

[sagesparrow]

Does anyone know...once you start taking exogenous T3, does your body temporarily stop converting T4 to T3 on it's own?

I'm wanting to quit my Cytomel (at least for now) to see if my palpitations go away. I'm anticipating some time of feeling crappy while I adjust...

Just curious how long it might take for my body to start producing it's OWN T3 from the T4 I take, so I can better gauge if stopping Cytomel is for me.

Thanks!

[flyingfool]

Rule of thumb is:

1) Ft4 to be 50% of the range and you are testing at 49%

AND

2) FT3 to be UPPEr 1/3 of the range or at least above 50% to 66.7%.  You are testing only at 37.5%.

So from this rule of thumb, your Free T4 is about dead on, but  you may not be converting well with the lower FT3 result.

i think you were pretty significantly overmedicated early on. And a zero to 25 mcg of T3 will throw most people into a tizzy!  25 mcg for a T4 medication is pretty common. But anything more than about 10 mcg of T3 seems to have many people have bad reactions.  This shows how inexperienced your Dr was.

I agree with Barb.  I think you need to stay right where you are at for several weeks and see how things settle out some. Unless your symptoms are just too aweful to deal with then by all means see your Dr and make some changes.  Otherwise staying the course and being patient is probably best.

[Barb135]

Your results ARE hypo.  Even the symptoms can be seen in hypo patients; as noted, I had anxiety, insomnia and palpitations when I was very hypo and the only thing that alleviated those symptoms was increasing my thyroid hormone levels.

Have you actually checked your HR at 140 after eating?  I used to feel like my heart was racing - I just knew it had to be going 200 or more and when I actually checked it, it was only 60 or 70... that's what anxiety can do to us...When this was first suggested to me, I thought the person was totally crazy, but as I paid attention, I realized they were right.  Are you only having the HR of 140 after eating?  If so, are you eating hot/spicy foods?  Those will increase your HR.  Otherwise, the HR might not be thyroid related and you should ask for a complete heart work up.  

Another thing to keep in mind is that it's very common for symptoms to worsen or for new ones to appear once you start one thyroid hormones or change meds/dosages.  Sometimes we have to ride out a few symptoms for a few weeks/months to see if they go away...

[sagesparrow]

Latest labs that I posted were on 10mcg cytomel. I understand that they look hypo... That's partially why I am confused, because I felt very hyper. The palpitations and HR of 140 after eating is not hyPO, is it? Maybe it's not due to thyroid, but these problems have only begun after starting medication.

[Barb135]

As you know, I've been away lately so haven't been on the forum much, until the past couple of days.  I was unaware of another, similar thread and you're right about losing context with multiple threads.  Having read the other thread, since you posted, I'm even more confused...

That FT3 is very low/hypo (only 38% of the range) for being on 25 mcg of cytomel, don't you think? Or is it 10 mcg, as stated in the other thread?    The FT4 is about right, at 49%, so I wouldn't change the T4 med.  Symptoms noted in the other thread (anxiety, insomnia and palpitations) can apply to either over or under medication... I had them all when very hypo.

[gimel]

I agree with your assessment.  Tried to convey the same recommendation in prior thread.  Yet another example of losing context when a member starts multiple threads.

http://www.medhelp.org/posts/Thyroid-Disorders/Help-with-latest-labs-and-symptoms--Im-so-confused--anxious/show/2254130#post_10839615

[Barb135]

When were these labs taken?  What medication(s) were on when they were done?  They indicate quite hypo, not over medicated.

[sagesparrow]

Hi Barb! Thank you for that last post... I asked my doc if maybe my levels were just too high for ME. and she said no, so long as I was in range I should not have symptoms. :/

Here are my latest labs:
TSH 0.017 (0.45 - 4.5)
FT3 2.9 (2.0 - 4.4)
FT4 1.32 (0.89 - 1.77)

[Barb135]

Just because your levels fell within the normal ranges, doesn't mean they were normal for you.  Can you please post the actual results of your tests, with reference ranges, so we can see where you are with it all?  That way, we can help you figure it out.

[sagesparrow]

Oh, and I got started on cytomel because my primary had no idea what she was doing. My Frees came back low after I ran some labs for fatigue, and she started me on 25 mcg Cytomel no Synthroid.

I felt great for a few weeks, then that went downhill and it was unstable. I took myself to an endo who started me on 100mcg Synthroid, but didn't factor in for the 25 mcg Cytomel...so I think I ended up overdosed.  I'm hoping this little detox experiment will get me to a better place, and if I am truly not converting, perhaps I can add cytomel back in VERY slowly.

[sagesparrow]

Thanks, Barb! My actual Frees were normal range last I checked and my TSH was suppressed to 0.01. I know that taking more T3 might be what I need... But I think I was having a reaction to the Cytomel? I've been off for two days now, and the palpitations and "grit my teeth" feeling has subsided. I'm also able to sleep again. I'm not sure how that is when my labs were in range...but perhaps I was spiking too high when taking the cytomel? Can't figure this stuff out yet.

[sagesparrow]

Thanks! I guess this little experiment will show how much I am truly converting... I only have about another 3-4 weeks til labs anyway. Hoping it's good news by then.

[Barb135]

What are your actual thyroid hormone levels?  While most people believe palpitations are only caused by too high levels of FT3, they can also be caused by not enough.  I had them when I was very hypo.  

Why did you start taking cytomel in the first place?

[Red_Star]

If you are taking T4 (besides your cytomel) then you will be converting that T4 to T3. How well you are converting T4 to T3 is another matter.