Avatar universal

Is it safe to get pregnant on NDT with suppressed TSH?

Hi everyone,

I am really hoping for some help. I have been on desiccated thyroid for a little over a year.  I am still dealing with fatigue though it's getting better at times. My question is now not about my levels themselves but about the safety of getting pregnant on NDT and with a suppressed TSH.  My current dosage is 150 mg erfa and my levels are:

- FREE T3 4.8 (3.5 - 6.5 pmol/L)

- FREE T4 15.8 1(0.0 - 25.0 pmol/L)


My doctor says he cannot say for sure if it's safe or not but feels that because my T3 and T4 are in the low range that perhaps my TSH isn't too far below the range. An endo I saw (and really disliked) told me that if I were to get pregnant now with these levels, I would almost guarantee a baby with birth defects.

I thought that TSH didn't matter on NDT and that what matters is free T3 and free T4 (though I know mine are still below the 50% and upper third range). Can anyone please shed some light on this?  I am already rather terrified of birth defects given that I am trying to conceive at age 40 and am just not willing to risk this if the risk is even remotely larger that I would have problems due to this hormone or my current levels.

I would really appreciate any help you can offer. I can tell you that this would be my second baby and that the first was born without complications. I did not know what my T3 was before my daughter was born but I believe I have secondary hypothyroidism because my TSH was always normal but my T4 was low and my T3 was below the range the first time it was ever tested.

Thank you.
8 Responses
649848 tn?1534633700
Are you sure the reference range for the Free T4 is 0.0-25.0?  If you had a Free T4 of 0, that would be way too low.  Typically, we see a range of something like 10-25 or 12-25, but not 0-25.  

Your Free T3 is only at 37% of its range and we, typically, recommend that Free T3 be in the upper half to upper third of its range.  You could actually use an increase in your ERFA, the way it looks.  

TSH is totally irrelevant when one is on replacement thyroid hormones, as it's a messenger to stimulate the thyroid and when the thyroid doesn't produce anything, TSH is useless.

If you have secondary hypothyroidism, that means there's an issue with the pituitary gland or the hypothalamus.  Have you had other hormones tested to make sure you don't have other issues?
Avatar universal

Thank you so much.  I did get the reference range wrong for T4.  I inserted a parenthesis in the wrong place.

I have had a lot of things tests over the past year.

May 2015  no meds TSH 1.21 (0.20-4) FT4 11.3 (10-25)  FT3 3.3 (3.5-6.5) TPO 13 (0-34)

July 15 30 synthroid     TSH 1.1                 FT4 11.9          FT3 3.5

Sept. 2015, 75 mg erfa    TSH 0.05                 FT4 15.7           FT3 4.6

October 25, 2015 DHEA-S 2.4 (1.5-13)

Nov. 25 120 erfa           TSH<0.01         FT4 6.9           FT3 20.9

Jan 6 2016 120 erfa TSH   0.01         FT4 18.8           FT3 6 Ferritin 130 (13-375)

March 2 120 erfa           TSH0.01                 FT4 17.3           FT3 5

CORTISOL AM 454 (200 - 690 nmol/L)
Cortisol PM 212 ((60 - 450 nmol/L)

April 18 180 erfa          TSH <0.01          FT4 18.6           FT3 6.1

June 9 150 erfa                TSH <0.01          FT4 16.4         FT3 4.9

June 23 150 erfa              TSH 45.4 >=12.1 nmol/L
RT3 was 18 (range is 8-25 ng/dl)

I've had other hormones done in the past for fertility testing  (mostly estrogen, progesterone, testosterone, etc.)and nothing was flagged as problematic (though I know that doesn't mean anything).  

If TSH is irrelevant does that mean it isn't a factor for causing birth defects?  The one endo scared the crap out of me and my current doctor isn't helping. I was thinking of raising my levels of erfa but I'm scared to do so now.
Avatar universal
I agree with Barb that you need an increase in your thyroid med, since your Free T4 and Free T3 are less than optimal and you have lingering hypo symptoms. Since hypo patients are so frequently deficient in Vitamin D, B12 and ferritin, you should make sure to test those and supplement as needed to optimize.  D should be at least 50, B12 in the upper end of the range, and ferritin should be at least 70.  B12 is especially important when you have fatigue symptoms.

I am not sure what the doctor said to scare you.  If it was about suppressed TSH indicating that you were hyper, rest assured that is not the case.  Our bodies evolved with low flow of thyroid hormone throughout the day.  When we take a single dose of thyroid med all at once, it suppresses TSH levels for an extended period.  That does not mean you are hyperthyroid, unless you have hyper symptoms due to excessive levels of Free T4 and Free T3, which is not the case for you.  There are scientific studies that showed that suppressed TSH was a common occurrence when taking adequate doses of thyroid med.  
649848 tn?1534633700
atalanta934... TSH is a pituitary hormone and its sole purpose is to stimulate the thyroid to produce thyroid hormones.  TSH neither causes nor alleviates symptoms.

You asked:  "If TSH is irrelevant does that mean it isn't a factor for causing birth defects?"  The answer is a resounding YES, that's what it means... low TSH is "not" a factor for causing birth defects!!  

Hyperthyroidism can cause problems during pregnancy, as can anti-thyroid meds, but you're only hyper if your Free T4 and Free T3 levels are too high and yours are not.  

On the flip side, adequate thyroid hormones are essential for the growth and development of a fetus; therefore, hypothyroidism "can" cause problems.  

You need higher levels of Free T4 and Free T3 than yours currently are...
Avatar universal
Thank you so much for these very helpful responses. I was scared to increase my dosage but will do so right away for my own sake and any possible pregnancy. I'm also determined to find a doc who actually knows what he/she is talking about.

With much gratitude,

Avatar universal
I'm back with a request for more help. Today my doctor sent me the following considerations:

1.  Fetal thyroid function does not come up to speed until around the 3rd trimester, so it is dependent on maternal thyroid support until then.
2.  Most neurocognitive development takes place in the 1st trimester.
3.  TSH is the preferred measurement in pregnancy as it is reliable.  The recommended targets are from 0.5 - 2.0.  TSH normal drops in the 1st trimester before rising up again in the 3rd trimester.  (Implication is that if one starts low, esp below 0.01, it is hard to follow how low the pregnancy will further push it down.)
4.  T4 results in pregnancy are difficult to interpret due to varying bound vs unbound to protein fractions.  (Implication is that FT4 is unreliable in pregnancy.)
5.  T3 does not cross the placental barrier and is generally not reflective of intracellular levels of T3.  (Implication is that T3 is not useful for measurement or supplementation in pregnancy.)

So, the action point I got out of all of this is that for ideal management forward in pregnancy, you should switch from dessicated thyroid to the pure levo-thyroxine formulation.  As you know the dessicated splits the supplement between T4 and T3, but if the T3 doesn’t pass through the placental layer, then it will not benefit the fetus.  A higher dose of levo-thyroxine vs the dessicated would provide a better dosing to the fetus.

The issues of hyper-supplementation to fetal development was not addressed.  However, known effects include possible miscarriage, fetal growth stunting and such.


So now I am freaking out. I would like to come back to him with some evidence, research, something that proves that I wouldn't have to switch to Synthroid. Can anyone help?  I do believe that views that you offer here but I need some proof to be able to convince the doctor.  Or should I just forget it and switch to Synthroid (which I don't want to do because when I tried it before it gave me headaches and made me forgetful).

Can anyone offer some help?

Thank you so much.
I'm on my way out the door, but will be back in a little while to more fully respond to your question.  But in short, your doctor is full of beans...
649848 tn?1534633700
Sorry I didn't get back here yesterday to address this... Your doctor is right on points 1 and 2... He gets off track on point # 3.  TSH should "not" be the preferred test during pregnancy or at any other time... Free T4 and Free T3 should always be tested.

From reading I've done, the best solution would be to add a small dose of Levothyroxine to your NDT, which will increase your FT4 level.  Many people on desiccate hormones have to add a small dose of levo anyway, since they often have too low FT4 levels, as do you.

It's recommended that Free T4 be maintained about mid range; yours is only at 39% of its range, so you need an increase anyway because you don't have enough for yourself, let alone, both, you and a fetus.  

At only 37% of its range, your FT3 is also lower than the recommended upper half to upper third of its range...

If you stay on the desiccated hormones and add some levo, you'll have the T3 you need, but you'll be adding T4 for the fetus...

Make sure your doctor tests Free T4 and Free T3, even though he doesn't think he needs to; if he refuses, you should find another doctor...
BTW... a fetus' thyroid begins working at about 12 weeks and about 18-20 weeks it will begin producing its own thyroid hormones.  At that point, iodine content in your diet is very important.  
Avatar universal
Hi Atalanta, I'd love to know if you were able to get pregnant, how this went and how this impacted your thyroid. I'm going through a similar situation to what you were in and I'm keen to understand how the story unfolded. Many thanks :)
Have an Answer?

You are reading content posted in the Thyroid Disorders Community

Top Thyroid Answerers
649848 tn?1534633700
Avatar universal
1756321 tn?1547095325
Queensland, Australia
Learn About Top Answerers
Didn't find the answer you were looking for?
Ask a question
Popular Resources
We tapped the CDC for information on what you need to know about radiation exposure
Endocrinologist Mark Lupo, MD, answers 10 questions about thyroid disorders and how to treat them
For people with Obsessive-Compulsive Disorder (OCD), the COVID-19 pandemic can be particularly challenging.
A list of national and international resources and hotlines to help connect you to needed health and medical services.
Here’s how your baby’s growing in your body each week.
These common ADD/ADHD myths could already be hurting your child