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The Surprising Cause of my Unexplained Infertility: My Thyroid

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[Disclaimer: I am not a doctor or medical practitioner. Any medical information is strictly my opinion based on research and personal experience, and not to be taken as advice. Always seek the advice of a licensed physician for your medical needs. Read my full disclaimer here.]

Could your thyroid be the cause of your infertility, even if doctors have previously told you that your thyroid levels were “normal”? It’s possible…and I think that was it for me.


The back story: I’ve been dealing with unexplained infertility for the last 2 1/2 years. (Read my story here.) I have had countless test done, with everything always coming back “normal.” For unexplained infertility, I’m a big fan of functional medicine — see more on that here.

So a couple of months ago I had my final appointment with my functional medicine doctor. After putting me on several different natural supplements, she had just re-run some bloodwork, and I was excited to get the results. I was convinced all of my levels would finally be optimal.

(Not that there were glaring issues before, by any means…hence the “unexplained” infertility label…but just some things that she thought could be even more optimal.)

One of those things was my TSH level. Although it was not out of range, several months ago it was at 3.3. Ideally, she told me, a level of 2.5 or less is optimal for getting pregnant (read the research on that below). So after putting me on a natural supplement for it, she tested it again several months later.

But though I was optimistic, when my doctor handed over my results, this one thing actually came back worse: my TSH level.

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My TSH level was now at 5.28. Oddly enough, after having gone on a natural thyroid supplement (called Thyrotain), my TSH levels actually increased, rather than decreased. My doctor then clinically diagnosed me with “hypothyroidism,” a known cause of infertility. Recognizing that a natural supplement was not working for me, my doctor prescribed me with a synthetic thyroid medication.

While I do wonder about the sudden increase in my TSH for seemingly no reason, that’s beside the point. Instead, let’s take a look at the role of TSH and fertility. (And find out how things ended up for me!) It could be your thyroid that is the cause of your unexplained infertility.

Thyroid (TSH Levels) + Infertility

According to most doctors, any TSH level below 5 is considered “normal.” In fact, at 3.3, previous doctors said nothing about thyroid being a possible cause for concern in terms of fertility.

The research, on the other hand, tells a different story. According to Jokar, TSH levels that are high — but still within the normal range — are associated with unexplained infertility. Although it’s not clear whether or not high-normal TSH levels cause unexplained infertility, the association is there. And like my doctor told me, a quick internet search reveals that it’s widely accepted that a TSH level of 2.5 (maximum) is optimal for fertility.

On the other hand: Recent studies (from 2017 and after) argue that 2.5 is too low. These recent studies have shown that treatment with thyroid medication has had no effect on fertility for women with a TSH level between 2.5 and 4.0. But at 4.0 or higher, thyroid medication does boost fertility. (There are some exceptions — see the research here to find out more.)

Either way, with my TSH level at 5.2, I think thyroid issues could be a contributing factor of my unexplained infertility.

How Did Things End Up for Me?

After being on synthetic thyroid medication for just two months, I got pregnant for the first time after trying for more than two and a half years. My TSH level 6 weeks after beginning medication was back down to 3.1; another 2 months later it was down to 1.7. Unfortunately, that pregnancy did result in miscarriage — read more on that here.

Moral of the story? If you’re dealing with unexplained infertility and a TSH level that is anything above 2.5, it’s worth asking your doctor about.


Also be sure to check out: 4 Other Possible Causes of Unexplained Infertility

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