Personal Case Study: Excess Estrogen Raises Thyroid Binding Globulin (TBG) - How Hormonal Birth Control Was Sabbotaging My Thyroid
A gynecologist, primary care physician (PCP) and endocrinologist all walk into a bar…
Oh wait, this wasn’t a joke, this was my real life. I had been to three doctors in a matter of months just to be told the same thing about the Hashimoto’s Diagnosis I had been given: “There’s nothing you can do, your condition is genetic and your body is going to attack your thyroid to the point at which it no longer functions at all. Hi, it’s you, you’re the problem and there’s nothing you can do about it. Oh, and by the way, once you have one autoimmune disease, prepare to develop others on down the line. Take this Levothyroxine and know that eventually you will rely solely on this medication because your thyroid will effectively be dead.”
Where do you even go from there? Once I was done ugly crying and asking “Why Me?” I got down to business. There was no way I was believing what I had been told, it just didn’t make sense. Rather than asking why, it was time to start investigating the what, when and how. My first stop? THE BIRTH CONTROL EXPERIMENT.
This chart documents my “Birth Control Experiment.” The red shaded areas represent time in which I was taking a combination birth control pill (Junel 1 mg - 20 mcg), the green shaded areas represent when I was off birth control. The blue bars are snapshots of my TSH (Thyroid Stimulating Hormone) through time (y-axis left) and the yellow line corresponds to my Levothyroxine dosage through time (y-axis right). Read below to learn more about my experiment!
After visiting “the thyroid specialist,” who was a conventional endocrinologist, I was told my thyroid prescription and lab testing could be managed by my PCP and that I didn’t need to come back to the endocrinologist until I developed diabetes. I. KID. YOU. NOT. I assured her she would never be seeing me again (yes, an absolute statement I knew was true). So, back to my PCP I went. My TSH (Thyroid Stimulating Hormone) in April 2015 was 6.63 uIU/mL while taking 75 mcg of Levothyroxine, so she bumped me up to 88 mcg, where I stayed until September 2015. I did not feel well, my TSH was still not optimal and I was looking for any way I could feel better. I was in the middle of selling and buying a house, planning a wedding, trying to keep my weight under control to fit in my wedding dress and working full-time in what was not considered to be a low stress job. I started dabbling around with dietary changes and asking very real questions about the impact my combination (synthetic estrogen and progestin) hormonal birth control pill was having on me and my thyroid. I was dismissed.
I was getting married in September 2015 and was desperate to feel better. I stopped taking my hormonal birth control pill and my levothyroxine dosage was increased to 112 mcg (yes, my doc skipped the 100 mcg level). In hindsight, the timing of these major shifts probably was not ideal, but I was desperate to feel better. Fast forward to January 2016 and my TSH was the lowest it had ever been at 0.925 uIU/mL. When I asked about birth control contributing to the drop, again I was dismissed and told it simply was because I was taking a higher dosage of Levothyroxine. I took the answer to my question and thought okay, if that’s true, I should be able to get back on birth control and all should be well with the world. <- Yes, there is a healthy dose of sarcasm and skepticism inserted here.
I started popping my daily hormonal birth control pill again and continued to take the 112 mcg of Levothyroxine. I went back in April 2016 to retest my TSH and it came back at 1.71 uIU/mL. It was higher than before, but not out of the realm of optimal. I went about my life maintaining my same routine of taking a daily combination hormonal birth control pill and daily Levothyroxine (112 mcg). By October 2016, my TSH had risen to 6.24 uIU/mL, again falling well outside the optimal range and even outside the lab’s “normal” range. Immediately, my PCP wanted to increase my dose of Levothyroxine up to 125 mcg. I refused and told her I wanted to stay at 112 mcg and that I would stop taking birth control pills again and just see what happened. She thought I was nuts and told me the two had nothing to do with each other, but she allowed me to be my own guinea pig.
I stopped taking hormonal birth control in October 2016 and maintained my Levothyroxine dosage of 112 mcg. I went back in March 2017 to re-test TSH and what do you know? It came back down to 1.91 uIU/mL without the need to increase my thyroid medication. Hormonal birth control had indeed been playing a role with what was going on with my thyroid. When I went to talk to my PCP about the results, she STILL vehemently denied they were related and said that I was “one of the few people it effects.” Needless to say, I stopped taking hormonal birth control in October 2016 and never looked back. Come to find out, this TBG phenomena I had discovered through my own experiment is actually well documented in the medical literature and package inserts for hormonal birth control. Apparently, my PCP, endocrinologist and gynecologist didn’t read those either…
https://www.accessdata.fda.gov/drugsatfda_docs/label/2012/021241s017lbl.pdf : Accessed 4/7/2024.
Above is a snippet from the Ortho Tri-Cyclen (combination hormonal birth control pill that I was taking at the time) package insert. I was getting medically gaslit before I even knew what it meant. If I had been provided true, informed consent, I would have had this knowledge without having had to experiment on myself.
What was actually going on?
High dose estrogen, by way of oral contraceptives or oral Estradiol Hormone Replacement Therapy (HRT), increases Thyroid Binding Globulin (TBG). TBG is a protein that binds up thyroid hormone and transports it throughout the bloodstream. When thyroid hormone is bound to TBG, it is inactive and not usable by the tissues. When TBG is high, this means there are low amounts of unbound, otherwise known as “free” thyroid hormones that can actually be used by the cells. When low levels of free thyroid hormone are detected in the system, the hypothalamus secretes TRH (Thyrotropin Releasing Hormone) to tell the pituitary gland there are low thyroid hormone levels in the system. Then, the pituitary gland secretes TSH (Thyroid Stimulating Hormone) to tell the thyroid to produce more thyroid hormone. These hormones are all on feedback loops with each other and are very intimately connected.
Estradiol has a proliferative effect on thyroid tissue. High estradiol will overstimulate thyroid tissue, subsequently increasing TBG. A high TBG means there is less free thyroid hormone that can be used by the cells and manifests in systemwide hypothyroid symptoms. It turns out our bodies and brains were designed perfectly and hold their own innate wisdom. When my brain was detecting low thyroid hormone in my system as a result of being bound up with TBG which was eleveated due to taking high dose estrogen (hormonal birth control pill) orally, the pituitary was sounding the alarm to my thyroid via TSH (Thyroid Stimulating Hormone) to produce more thyroid hormone. The signal would get louder and louder through time. When estrogen was reduced in my system (by removing hormonal birth control from the equation), TBG would also decrease and free up more thyroid hormone to be used by my cells and would calm the alerts from my pituitary gland (TSH would come back down). Stopping hormonal birth control was a major victory in my hormonal healing journey, but it was only one piece. It turns out autoimmune disease can be much more complicated. This was my starting point.
Note: If oral estrogen is the only option for a particular woman, it is imperative to understand these feedback loops to manage care going forward. Additionally, estrogen detoxification is critical to addressing this issue in women who choose to continue to take oral hormonal contraceptives or HRT.
Years later (2019), I was reading Dr. Jolene Brighten’s book Beyond the Pill and finally felt seen, heard and validated. There is a section in Chapter 7 titled How the Pill Sabotages Your Thyroid and the first sentence of the section reads “There is a very real connection between the pill and your thyroid. In fact, many of my patients notice their thyroid problems began after they started taking birth control.” The birth control pill was depleting vital nutrients necessary for my thyroid to synthesize thyroid hormone and for my cells to uptake the hormones themselves. I was making less thyroid hormone, converting even less to its active form (T4 -> T3) and the little conversion that was taking place struggled to actually be used by my cells. All resulting in me being and feeling hypothyroid but chalking it all up as being “normal".”
