Metformin and Your Thyroid


Receiving an autoimmune diagnosis can be challenging for the best of us. It can literally take years of searching for answers to seemingly unrelated symptoms to receive a diagnosis to confirm what’s wrong. However, conventional treatment of Hashimoto’s and other autoimmune diseases can leave little hope for improvement. Treatment for secondary conditions like type II diabetes can lead doctors to treat the symptoms and not the underlying root cause.  Metformin is one of the most commonly prescribed drugs for regulating blood sugar, but did you know that it can suppress TSH?  If your doctor is unaware of the connection, a change in your TSH level can result in him or her wanting to reduce the dose of your thyroid medication. So, if you are taking metformin and thyroid replacement for Hashimoto’s, the good news is that being informed of this very important detail will allow you to talk with your doctor with the goal in mind to not reduce your thyroid medication simply based a low TSH level that is likely being driven by metformin.

What is Metformin?

Metformin is a popular medication for patients with type II diabetes and polycystic ovary syndrome (PCOS). It is used for gestational diabetes also. It may be called Fortamet, Glucophage, Glucophage XR, Glumetza, and Riomet. Metformin helps regulate blood sugar and has been a favorite prescription in the United States since 1995. While it may be an appropriate medication for patients with Hashimoto’s and many conditions, it’s essential to note that it can lower TSH to below-normal levels.

Typically, doctors will test TSH only or TSH and Tr only, as opposed to testing TSH, Free T3, Free T4, Reverse T3, and thyroid antibodies.  In some cases, the TSH level may detect a thyroid problem, but not always.  The TSH is mainly a marker for pituitary function.  It is essential to test Free T3 and Free T4 levels before adjusting your medication, never on the TSH alone.  Your TSH level only shows you one piece of a larger picture. The TSH level is often influenced by other treatment you may be undergoing. Before being diagnosed with Hashimoto’s, I struggled with symptoms for years, and my TSH was in the “normal” range.

You DO Have Control!

I’ve written in the past about the importance of requesting the correct labs for thyroid testing. I’ve worked hard to convince doctors who were my trusted colleagues and friends to consider testing more than just TSH and T4. Sadly, until you’ve lived with Hashimoto’s or another autoimmune condition, it can be hard to understand the frustration of “normal” lab work results when you know there is an imbalance in your body.  Thr truth is there is a significant difference between “normal,” and “optimal.”  We want optimal!   If your doctor doesn’t want to order a more comprehensive lab work panel, you’re not out of options! You have the choice to pay out of pocket and order these yourself, at minimal cost through labs such as this one.

An important part of daily living as a Hashi’s sister is knowing that you do have control. We all have days where we feel like our bodies have a mind of their own. Take time to record the symptoms you’re experiencing in these moments and listen to what your body is telling you. If you’ve received a test result that doesn’t reflect how you’re feeling, keep searching. I would never be where I am today if I would have just accepted my doctor’s diagnosis and treatment plan. Request copies of all of your medical records. Keep your labs in a notebook and don’t ever accept a verbal report of your results. This is how you detect subtle changes in your numbers over time.  This is very important.  Learn about the different thyroid hormones, and what they look like in terms of lab values when you’re at your best and your worst. Remember that Hashimoto’s is not a thyroid disease, but an autoimmune condition. It has an R&R pattern:  relapse and remit; and we often have more than one condition going on, like high blood sugar, high cholesterol, high blood pressure, or other autoimmune conditions.  By knowing your body well, you have the power to achieve optimal health and better quality of life no matter what your diagnosis.