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.100 versus .112 Synthroid. Advice Needed!

Is there any benefit to taking .100 mcg Synthroid 7 days per week as opposed to .112 mcg 6 days per week?  I have the option of either and don't know what to do. Thanks.
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Avatar universal
I suggest that you print off 2 copies of the research paper below. Read one and give a copy to your doctor. This is a recent paper (2018) and your doctor obviously has not seen it.

The paper has two major conclusions:
1. TSH should not be used to gauge the adequacy of your Synthroid medication, and
2. FT3 should be used to gauge the adequacy of your Synthroid medication.

The paper advocates an emphasis on treating your symptoms, and states, "optimum therapy may be best approached by maintaining adequate FT3 levels and, if required for symptom relief, elevating FT3 above the median, but still remaining within the reference range." They go on to say, "...all three parameters TSH, FT4 and FT3 and their interrelations should be considered for dose adequacy."

If you are still suffering from fatigue on 112 mcg Synthroid, then this paper would suggest you need to take more, not less.

The paper:
Symptomatic Relief is Related to Serum Free Triiodothyronine Concentrations during Follow-up in Levothyroxine-Treated Patients with Differentiated Thyroid Cancer.
Larisch R, Midgley JEM, Dietrich JW,, Hoermann R.
Exp Clin Endocrinol Diabetes. 2018 Sep;126(9):546-552. doi: 10.1055/s-0043-125064. Epub 2018 Feb 2.

A PDF of the research paper can be downloaded from:
Helpful - 0
Thank you.  I had labs done in Oct. 18 and my TSH was 0.07 uIU/mL (Standard range is 0.35 - 3.30 uIU/mL).  My T4 was 1.61 ng/dL (standard range is 0.56 - 1.64 ng/dL) and my  T3  was 2.6 pg/mL( standard range is 1.7 - 3.7 pg/mL).  They said my TSH was too low and had me take .112 mcg of Synthroid only 6 days per week for 6 weeks.  After that my TSH is now 0.30 uIU/mL and my T4 is 1.08 ng/dL.  They told me my TSH is target level now and I can either do  112 Synthroid 6 days per week or 100 Synthroid daily.
Avatar universal
Most doctors don't recognize the huge difference between a suppressed TSH in the untreated state versus during treatment.  TSH suppression is a typical occurrence when taking  significant, once daily doses of thyroid medication.  That does not mean hyperthyroidism unless there are accompanying hyper symptoms due to excessive levels of Free T4 and Free T3, which certainly is not your case.  

telus2 referenced an excellent scientific study.  The study is the first I have ever found that quantified the effect of Free T3 level on the incidence of hypothyroid symptoms.   Fig. 1a suggests that Free T3 should be in the upper third of its range.     The authors state, "  While rates of both hypothyroid or hyperthyroid symptoms were significantly related to all three thyroid parameters, the relationship of hypothyroid symptoms with FT3 extended to a below reference TSH range. Hypothyroid symptom relief was associated with both a T4 dose giving TSH-suppression below the lower reference limit and FT3 elevated further into the upper half of its reference range. In multivariable analysis, relationships between complaints and FT3 concentrations remained significant after adjusting for gender, age and BMI."  Also, "Residual hypothyroid complaints in LT4-treated
patients are specifically related to low FT3 concentrations. This supports an important role of FT3 for clinical decision making on dose adequacy, particularly in symptomatic athyreotic patients."

The 112 mcg dose of T4 is not significantly different than 100 mcg 7 days a week.  I think I would choose the 100 daily, just to be consistent and make it easier to remember daily.  The bigger issue is getting your Free T3 high enough to relieve any hypo symptoms that you have.  So pleases tell us about any symptoms.  also, what was the identified cause for your hypothyroidism?

If you want to read about TSH suppression, click on my name and then scroll down to my Journal and read at least the one page Overview of a paper on Diagnosis and Treatment of Hypothyroidism:  A Patient's Perspective.   In the full paper, Rec. 13 on page 13 you will find corroborating info about TSH suppression being a common occurrence when taking thyroid med, and not a reason to reduce the med dosage.  
Helpful - 0
Thank you for this detailed info.  I had thyroid cancer and a TT 3 years ago.  I've been on 112 Synthroid ever since.  I still have three cancerous lymph nodes (1 confirmed, 2 suspected) that are being monitored with ultrasounds and bloodwork because RAI supposedly won't effect them enough to justify the radiation.  I feel chronically fatigued and I barely get my period post-op.  The same doctors who pressured me into the TT telling me I had a serious health issue are now annoyed that I present with symptoms.  Apparently thyroid cancer is only serious if you don't have surgery, but once you do it's a minor health issue barely worth mentioning according to the medical community.  I guess I didn't get the memo.  

I think I will switch to .100 mcg just to see if it makes a difference at all.  Thank you.
Avatar universal
The most important thing is to get your doctor to add some T3 to your meds and then raise the dosage enough to get your Free T3 into the upper half of its range.  If the doctor refuses, then you need another doctor that will do so.  In addition, hypothyroid patients are frequently deficient in Vitamin D, B12 and ferritin.  So you need to get those tested and then supplement as needed to optimize.  Vitamin D should be at least 50 ng/mL, B12 in the upper part of the range, and ferritin (a  storage form  of iron that the body can readily use)  should be at least 100.  I also suggest testing for cortisol, since if affects thyroid.
Helpful - 0
Thank you gain for your response.  What meds would increase my free T3?  I have an apt. with my endo in late January.  I run out of my  112 Synthroid in two weeks.  Do you recommend I switch to 100 for now and then discuss adding the T3 at my apt.?  I was going to cancel my apt. but maybe I should keep it?  My endo is a young resident but he and his attending seem reasonable and willing to discuss options with me.
Avatar universal
Before I mention anything else, I want to emphasize that you should always delay taking your morning thyroid med until after the blood draw, in order to avoid false high results.  This is even more important if you start taking T3 type meds, since they affect serum levels even faster than T4.  

If it were me I would go to 100 daily, which will be only a small increase of less than 4 mcg daily.    The biggest need is getting your Free T3 into the upper third of its range, and then tweaked from there to relieve symptoms.   T3 med is called liothyronine, brand name Cytomel, and there are generics.   IF you can get the Endo to do this, then a good starting dose would be 5 mcg for a few weeks and then increase to 10 mcg for another 2-3 weeks and then re-test Free T4 and Free T3.  

Since hypo patients are so frequently deficient in Vitamin D, B12 and ferritin, those need to be tested and supplemented as mentioned previously.  It would also be a good idea to test for cortisol.  

The more knowledgeable you become about all this the better success you will have getting your doctor to do what is needed.  So I suggest that you click on my name and then scroll down to my Journal and read at least the one page Overview of a paper on Diagnosis and Treatment of Hypothyroidism: A Patient's Perspective.  It would also be a good idea to give a copy to the doctor to help get what you need.
Helpful - 0
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