If you’re ballooning out since your endo diagnosis, a gland to consider investigating besides your ovaries is your thyroid. This cute, butterfly-shaped gland in your neck produces hormones that regulate the body's metabolism. These hormones are crucial for growth, development, and maintaining overall energy balance.

When this glad is off-kilter, you may be diagnosed with hyperthyroid (think hyper, overactive) or hypothroid (slow, underactive). Unfortunately, both are associated in certain ways with endometriosis.

However, for the focus of this blog (because a deep dive into the endo-thyroid connection would turn this “quick read” into a novel), we will touch on the link between hypothyroid, endometriosis and weight gain.

What is Hypothyroid, and How Can It Cause Weight Gain?

When your thyroid gland slows down, it’s called hypothyroid, and can happen due to numerous reasons. The big ones include Hashimoto’s (an autoimmune disease that attacks the thyroid gland) or Primary Hypothyroidism, where the problem originates in the thyroid gland itself rather than being caused by external factors like autoimmune diseases. Causes include iodine deficiency, certain medications, radiation therapy, or congenital issues.

Either way, when the thyroid gland slows down, it produces fewer thyroid hormones—the hormones necessary for energy and metabolism. This is why people with hypothyroidism experience symptoms similar to a power outage: cold hands and feet, muscle weakness, poor cognitive function, constipation, dry skin, fatigue, hair loss, and even menstrual pain.

Oh, and weight gain!

These symptoms happen because the thyroid hormones that regulate energy expenditure are deficient. In the case of weight gain, a decreased metabolic rate leads to reduced calorie burning, which can result in weight gain even if dietary intake remains the same.

Super bummer on a lot of levels

The Association Between Endometriosis and Hypothyroid

While endometriosis doesn’t appear to cause hypothyroid, or vice versa, there does seem to be an association. For example, one study demonstrated that women with endometriosis are 6x more likely to have Hashimoto’s than those without endo. [1] That’s a lot more! While this study doesn’t investigate why, exactly, we do know that autoimmune and endometriosis develop along similar circumstances: a combination of genetic, immune, hormonal, environmental, and lifestyle factors. Thus, hypothyroidism and endometriosis may be associated due to shared underlying mechanisms.

In fact, they are so commonly associated that they’re sometimes referred to as “sister diseases,” which I mention in my book (see picture).

In my book, I mention they're sometimes referred to as sister diseases.

Beyond the direct associations between the diseases, you can see the overlap in symptoms. How many of us could put a check mark next to a few of those I listed above: cold hands and feet, muscle weakness, poor cognitive function, constipation, dry skin, fatigue, hair loss, weight gain, and menstrual pain? I know in my client base, it was a lot of folks!

Uncovering Your Unique Thyroid Health

If you think you may have thyroid issues, please don’t just guess! Understanding exactly what’s going on with your thyroid (if anything at all) is imperative to your healing journey. I mean, imagine if you thought you had a thyroid issue for years to find out you never did? Conversely, imagine if you never tested and dealt with symptoms for years when something like supplementing with thyroid hormone could have tunred your life around.

So, what’s a gal to do? Test :)

Luckily, finding out if you have Hashimoto’s is relatively easy with a blood test. Through a Thyroid Antibody Tests you can easily measure anti-thyroid peroxidase (TPO) antibodies, which help identify autoimmune thyroid conditions like Hashimoto's thyroiditis.

You can uncover more hypothyroid issues through other tests:

Thyroid Function Tests: Blood tests measure levels of thyroid-stimulating hormone (TSH) and thyroxine (T4). Elevated TSH and low T4 levels generally indicate hypothyroidism.
Thyroid Ultrasound: This imaging can check for abnormalities such as nodules or inflammation.
Radioactive Iodine Uptake Test: This test measures how well the thyroid gland absorbs iodine, which can help differentiate between different types of thyroid dysfunction.

On another testing note, I am a huge fan of Hair Tissue Mineral Analysis (HTMA) for further investigation of how the thyroid is functioning. I talk a little bit more about that here.

What Can Be Done Before I Gain Weight Forever?

Great question! And the answer will depend on what you uncover about your own body, and why you have an underperforming thryoid.

For example, some people with extensive thyroid damage may not be able to make enough thyroid hormones on their own. In this case, Thyroid Hormone Replacement Therapy (i.e., taking synthetic thyroid hormone levothyroxine, T4) would be the most common and effective treatment. This would help normalize hormone levels and alleviate symptoms.

Of course, as a Nutritional Therapist, I must say there are many other ways to help! Please don’t become too fixated on one thing as a “quick fix” when we know that both endometriosis and hypothyroid are often multifactorial (i.e. occur due to many factors, so require addressing those factors to heal]

Endometriosis hypothyroid nutrient dense foods — Eating nutrient-dense foods rich in fatty acids, vitamins, amino acids, and minerals -- and low in sugar -- can be a great place to start when seeking quick wins!

Addressing Underlying Causes: If hypothyroidism is due to factors like iodine deficiency or inflammation, addressing these underlying issues can improve thyroid function.
Lifestyle and Dietary Adjustments: Adopting a balanced diet rich in nutrients that support thyroid health (e.g., iodine, selenium, and zinc), reducing toxin load, managing your nervous system state can contribute to overall well-being and reduce inflammation
Read my book, Heal Endo! This book is literally all about reducing inflammation, increasing nutrient intake, and aiming to stop diseases like endometriosis (and Hashimoto’s) in their tracks.

So, In This Case, Does Endometriosis Cause Weight Gain?

If you have hypothyroid along with your endometriosis, then you definitely could have some weight gain (fat gain, to be specific) that occurred thanks to a body-wide power outage.

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1) Sinaii N, Cleary SD, Ballweg ML, Nieman LK, Stratton P. High rates of autoimmune and endocrine disorders, fibromyalgia, chronic fatigue syndrome and atopic diseases among women with endometriosis: a survey analysis. Hum Reprod. 2002 Oct;17(10):2715-24. doi: 10.1093/humrep/17.10.2715. PMID: 12351553.