Fatigue, Brain Fog, Hair Loss and Weight Gain
Is it perimenopause, or is it your bitchy little thyroid?
Fatigue, brain fog, and hair loss are common during perimenopause and can be incredibly debilitating. And while we all know the BMI is absolute bullshit and beauty standards can fully get fucked, an increase in stored fat around the mid-section is a concern for many of us due to the health implications, particularly those of us with diabetes, heart disease and dementia in the family.
Naturally, the first person to speak to when you’re experiencing these symptoms is your doctor. But if you’ve done that already and have been told everything is fine, it may be time to do your own research. You’re not an idiot: if you feel like shit and have a clusterfuck of symptoms, you clearly aren’t fine — it just means they haven’t found the problem(s). Also, more knowledge means you can initiate the right conversations.
The fact is that perimenopause symptoms and the symptoms of an underactive thyroid have some massive overlap, so it’s worth looking into whether your symptoms are to do with perimenopause, your thyroid, or a combination of both. On that basis, this is Part I of a 2-part series. While this part focuses on the thyroid, the second part will take a deep dive into what the experts say about unfucking your hormones in perimenopause — specifically progesterone and estrogen.
Understanding Thyroid Hormones
An underactive thyroid can lead to hair loss, fatigue, brain fog and weight gain. Note that an overactive thyroid can also lead to hair loss, but it will usually come with weight loss rather than gain. Here’s a quick overview of the main thyroid hormones TSH, Free T3, and Free T4 and their optimal levels according to thyroid expert Dr. Izabella Wentz Pharm.D1:
TSH: Thyroid Stimulating Hormone (TSH) is made by the pituitary gland. When your thyroid gland is making enough (or too much) thyroid hormone, it signals the pituitary gland to make less TSH. When your thyroid gland is making too little thyroid hormone, it signals your pituitary gland to make more TSH. Therefore there’s an inverse relationship between TSH and thyroid function, with high TSH suggesting an underactive thyroid (hypothyroidism) and low TSH suggesting an overactive thyroid (hyperthyroidism).
According to Dr Izabella Wentz, the ideal range for TSH is between 0.5 - 2 μIU/mL (0.5 - 2 mIU/L) for a healthy adult not taking thyroid medications. Most naturopaths and functional doctors, including Dr Wentz, advise that TSH should not be looked at on its own.
Free T4 & Free T3: T4 (Thyroxine) and T3 (Triiodothyronine) are two of the main thyroid hormones. These hormones play an important role in regulation of weight, energy levels, internal temperature, skin, hair, nail growth, and metabolism. T4 is known as prohormone, i.e. a committed precursor of a hormone that has minimal hormonal effect by itself. It is considerably less biologically active than T3. Most of the commonly prescribed thyroid medications like Synthroid, Levothyroxine and Tirosint only contain T4 (Thyroxine), and therefore need to be converted to the active T3 form in the body. As Dr Izabella Wentz explains: “On paper, the T4 to T3 conversion happens just fine, but in the real world, in real human bodies, we may not always convert T4 to T3.”
The ideal range for T4 is between 15 - 23 pmol/L, with lower levels indicating an underactive thyroid (functionally hypothyroid). The ideal range for T3 is between 5 - 7 pmol/L. Lower levels can indicate an underactive thyroid (functionally hypothyroid).
Which thyroid hormones do doctors check?
Under the current guidelines, many doctors won’t look at any further thyroid testing unless your TSH is below 0.4 mIU/L or above 3.5 mIU/L (different labs may have slightly different ranges). If TSH is high or low according to their standard ranges, only then will they test further.
According to most (if not all) functional doctors and naturopaths, TSH on its own doesn’t always give you the full picture. The problem is that you could have an insufficient amount of thyroid hormone actually reaching your cells despite having normal TSH, which would be indicated by having low Free T3 and/or low Free T4.
Unfucking functional hypothyroidism:
Some recommended ways to treat functional hypothyroidism due to lower than optimal T3 and T4 are:
Make sure your vitamin D levels are optimal. Between 60 ng/mL to 80 ng/mL (150 - 200 nmol/L) is what Dr Izabella Wentz recommends for optimal thyroid receptor and immune system function. If you’re supplementing with D3 it’s important to take K2 and magnesium as well. Note that D3 is a fat soluble vitamin, so it needs to be taken with foods that contain fat.
Make sure your ferritin is optimal. Ferritin is important in our body’s ability to utilize T3, which is necessary for our thyroid health, which in turn affects our energy levels and hair growth. The optimal ferritin level for thyroid function is between 90-110 ng/mL. When it comes to hair loss, Dr Wentz states that ferritin levels of at least 40 ng/mL are needed to stop hair loss, and that a level of at least 70 ng/mL is needed for hair regrowth. Never take iron supplements without checking your iron levels first, since iron overload is dangerous.
Make sure your B12 is optimal: Lara Briden states a healthy vitamin B12 level should be at least 400 pg/mL (295 pmol/L)2. If you take a B12 supplement, choose an activated form (i.e. methylcobalamin rather than cyanocobalamin), especially if you have the common MTHFR gene mutation.
Make sure your Zinc and Copper are optimal: Zinc is essential for the synthesis and activation of thyroid hormone. According to Lara Briden, plasma zinc should be 11 - 23 µmol/L (70-150 µg/dL). Dr Dale Bredesen recommends 90 - 110 ug/DL (14 - 17 µmol/L)3. Note also that your blood work should show a Zinc to Copper ratio of approximately 1:1, so equal amounts of zinc and copper4. High copper is linked to dementia risks.5 If your copper levels are higher than your zinc levels (but not so high that your doctor is concerned), taking a 30 mg zinc supplement will help lower it. No need to go nuts because both minerals are important.
Take Magnesium: Magnesium supports the thyroid, calms the nervous system, regulates the HPA axis, reduces blood sugar, helps to normalise insulin, and is also anti-inflammatory, which helps to quiet the autoimmune inflammation that underlies most thyroid disease. Lara Briden says to opt for magnesium glycinate, bisglycinate, or threonate. Maybe skip the magnesium oxide; a 2019 study found it had the lowest bioavailability.
Take Selenium. Selenium is a key nutrient for the thyroid and immune system, as it reduces inflammation and oxidative stress in the thyroid gland6. Selenium also aids with the conversion of T4 to T3. The therapeutic dose is 100-150 mcg per day from all sources7. Too much is toxic, so if you are eating high selenium foods such as Brazil nuts, you need to take this into account.
Take Iodine: Iodine is important for thyroid health, the immune system, eyes, brain, ovaries and breasts8. It acts to reduce inflammation and promote estrogen metabolism, and it can therefore be helpful for ovulation pain, ovarian cysts, fibroids, premenstrual mood, and breast pain. Lara Briden prescribes ranges for her patients from 250 mcg to 3000 mcg depending on the baseline health of their thyroid; she states that those who have positive thyroid antibodies should “probably not take more than 500 mcg”9. Dr Izabella Wentz explains that a daily dose of 200 mcg per day can reduce TgAB and TPO antibody levels, which is a good thing (more on that below), while very high doses can have the opposite effect. I personally take a 225 mcg supplement since I have thyroid antibodies (This brand of iodine was recommended to me by a one-of-a-kind GP who is very knowledgeable in women’s health and functional medicine). Note that if you supplement iodine you should also take selenium.
Reduce TPO / TgAB antibodies: Thyroglobulin antibodies (TgAb), and Thyroid peroxidase (TPO) antibodies will ideally be below 2 IU/mL. Lowering thyroid antibodies can improve thyroid function. Dr Izabella Wentz states that when people start developing thyroid antibodies, they may start to exhibit a number of different non-specific symptoms like fatigue, anxiety, stress, miscarriages, hair loss, and weight gain. She states that selenium and myo-inositol have been shown to reduce thyroid antibodies, along with the appropriate amount of iodine. A 2016 study found that Vitamin D supplementation reduces TPO antibody levels in patients with autoimmune thyroid disease. Another thing to consider is going gluten free; a 2023 meta-analysis indicated a positive effect of the gluten deprivation on thyroid function and its inflammation, particularly in patients with Hashimoto’s and Graves disease.
Consider taking Myo-Inositol. Research has shown that myo-inositol and selenium supplementation reduces thyroid antibody and TSH levels. This randomised controlled trial in 2015 found that myo-inositol also improves PCOS symptoms such acne and insulin resistance.
Consider taking L-Tyrosine. Tyrosine, an amino acid found in various high protein foods, is a precursor of the thyroid hormone thyroxine and several neurotransmitters (dopamine, norepinephrine). L-tyrosine has been found to enhance positive mood and cognitive function, especially in situations involving stress. L-Tyrosine isn’t recommended if you’re already on thyroid medications, or if you have an overactive thyroid. I took 500 mg of L-Tyrosine in the morning for a few days and it gave me a big dose of energy but made me feel jittery, which can happen to people who are sensitive to stimulants.
Consider taking NAC: Research suggests that NAC may support the thyroid due to its anti-inflammatory effect. NAC’s ability to replenish glutathione and regulate brain glutamate levels can also boost memory. I personally found NAC to be extremely helpful in reducing perimenopausal brain fog, and there have been some discussions around NAC and reduction in brain fog for people with long COVID.
Consider a thyroid supplement (or not): Most thyroid supplements will contain B12, iodine, zinc, selenium, which are all great. Many will contain L-Tyrosine, which is fine. But some also contain copper, which will be harmful if you already have high levels. Another issue with thyroid supplements is that you can’t isolate what’s working for you and what isn’t, for example if you find that you are too sensitive to L-Tyrosine. The vitamin doses may also not be at the right levels for you, and the B12 may not be in active form.
Reduce stress: I know the advice to “reduce stress” sucks arse because most of us feel as though stress isn’t something we can control. But while we can’t change what happens, we can change the way we think about what happens. I found my stress levels reduced when I learned to practice more acceptance of the world around me, and when I started deprioritising work (I still work hard but I refuse to make it the centre of my life, or to prop myself up with sugar and work ridiculous hours so that a corporation can make more money while I atrophy at my desk). Getting enough sleep, not overdoing the exercise, and not going on any extremely low calorie diets will also help.
Consider chatting with your doctor about thyroid meds. If you’re functionally hypothyroid you can probably change things naturally by supporting your thyroid through the ways listed above, but if things don’t improve or get worse, this info may be useful when chatting with your doctor. As I mentioned, the most common thyroid medication is a synthetic version of thyroxine, which is T4 (common brand names are Synthroid, Levoxyl, and Tirosint). T4 works for many people but not everyone, particularly if their body isn’t efficiently converting the T4 into T3. If your T3 is low you might want to discuss taking a T4 and T3 combination like Natural Desiccated Thyroid (NDT). In rare cases some people take T3 only.
Increase progesterone naturally / take progesterone if you need it: According to this placebo-controlled 12-week trial, progesterone therapy increases free thyroxine (T4) levels. Progesterone is the first hormone to drop during perimenopause, followed by estrogen at a later stage. According to Lara Briden, the only way to make progesterone is to consistently ovulate every month (and just because you have a period doesn’t mean you’re ovulating). Her general ovulation strategies include: Correcting underlying inflammatory issues (if you have them) such as dairy sensitivity, gluten sensitivity, mast cells and histamine issues, leaky gut, and insulin resistance; being fully nourished with calories, protein, carbohydrates, fat; and reducing stress. Nutrients such as cholesterol, B vitamins, coQ10, vitamin D, iodine, selenium, magnesium, and zinc are also important for ovulation. You can also take body-identical progesterone.
Reverse insulin resistance: Lara Briden states that healthy fasting insulin should be less than 10 mIU/L (60 pmol/L), however she also states that “it’s probably not possible to lose much abdominal weight, or abdominal fat, until fasting insulin comes below 8 mIU/L”. Dr Dale Bredesen states that fasting insulin for optimal metabolic health should be 3.0 - 5.0 uIU/mL (3.0 - 5.0 mIU/mL).10 Reversing insulin resistance involves eating more whole foods, avoiding sweet drinks, reducing processed carbs, supplementing magnesium, maintaining a healthy circadian rhythm (go to bed on time and get morning sunshine), and moving more. An interesting 2022 meta study in the Sports Medicine journal found that light-intensity walking in short 2 - 5 minute bursts significantly improved insulin levels after meals compared to prolonged sitting and standing breaks.
That’s it for now. Hopefully this information saves you a little bit of time and will lead to some important conversations with your health care providers. If you found this article useful, please click the heart down the bottom left of this page (it helps other people find my work, and it also makes me feel all warm and fuzzy). Note that part II on estrogen and progesterone will be a few weeks away, I need to focus on some non-Substack writing projects. Please remember that you should always speak to your health professional before making any dietary or lifestyle changes; this is general information not specific to your situation.
Dr. Izabella Wentz Pharm.D is trained in functional medicine through The Institute for Functional Medicine, Kalish Functional Medicine, and the American Academy of Anti-Aging Medicine.
Hormone Repair Manual: Every Woman’s Guide to Healthy Hormones After 40, by Lara Briden, page 182.
The End of Alzheimer’s Programme, by Dr Dale Bredesen, pages 22 & 185.
This doesn’t mean you should take equal amounts of copper and zinc (You absolutely should not). This is about interpreting blood test results, not determining supplement dosage.
The End of Alzheimer’s Programme, by Dr Dale Bredesen, page 184.
Hormone Repair Manual: Every Woman’s Guide to Healthy Hormones After 40, by Lara Briden, page 217.
Hormone Repair Manual: Every Woman’s Guide to Healthy Hormones After 40, by Lara Briden, page 217.
Hormone Repair Manual: Every Woman’s Guide to Healthy Hormones After 40, by Lara Briden, page 135.
Hormone Repair Manual: Every Woman’s Guide to Healthy Hormones After 40, by Lara Briden, page 136.
The End of Alzheimer’s Programme, by Dr Dale Bredesen, page 21.
Thanks so much for sharing this work, Denise. My ferritin was low on my last blood test, but I wonder if that might have had to do with where I was in my cycle -- I had been bleeding the past seven days. 🤔
Thanks for sharing this! I’ve been researching the topic as well because a few months ago my sleep was totally fucked and I was experiencing night sweats. I thought maybe it was perimenopause, although I don’t want to self-diagnose (I’m only 39, turning 40 in a few months, so might be a little early, or maybe that’s just denial speaking?). I still need to go to my GP for a blood test (this was a good kick in the ass to do so), but I started taking B12, Magnesium, and vitamin D (until it became sunnier again here in AMS), and so far, it has helped! Excited for part 3 of this series!