The Thyroid-Fertility Connection You Need To Know About

Many women have a sense that there is something wrong with their thyroid health—they're gaining weight despite a healthy diet, experiencing chronic fatigue or cold intolerance, losing hair, forgetting things, having trouble going to the bathroom, and feeling generally depressed—and yet no one has ever done a comprehensive thyroid evaluation on them.

The reason this is so frustrating? We know that thyroid disorders are incredibly common, affecting one in 10 women, and that about 60% of people with a thyroid problem are unaware of their condition—and thus, unable to manage it appropriately. This is particularly heartbreaking in the context of fertility struggles, which may be a symptom of an unmanaged thyroid issue that conventional medical practitioners miss, thereby leading many women down a stressful path of potentially unnecessary fertility tests and treatments.

Hypothyroidism (or low thyroid function), especially the common autoimmune type called Hashimoto's thyroiditis, is often missed as a hidden cause of fertility struggles and pregnancy loss. The fact is, the thyroid affects our reproductive system in a big way. Thyroid hormones are important in the regulation of the menstrual cycle, and imbalances in these hormones can cause amenorrhea (no periods) or irregular cycles, impair ovulation (making it difficult to conceive), and affect progesterone levels1 (increasing the risk of pregnancy loss). And research supports this thyroid-fertility connection quite clearly: One study2 found that 76% of infertile women with hypothyroidism were able to conceive within six weeks to a year of receiving treatment for their thyroid condition.

It's estimated that the prevalence of "subclinical hypothyroidism" (not quite full-blown hypothyroidism) in non-pregnant women of childbearing age is 4% to 8%, and these numbers likely underrepresent the problem. And knowing that you have high thyroid antibodies can be the first step in a holistic approach to increasing fertility—in the early stages of Hashimoto's, the thyroid's function may be variable and work well once a patient makes strategic lifestyle and dietary changes.

What I've found in my professional experience is that it's surprisingly common for a woman to have had a full invasive fertility work-up (think: having dye injected into your cervix so doctors can take pictures of your fallopian tubes, undergoing painful biopsies and cultures of your uterus, and undergoing extensive blood tests of other kinds) without first having a full thyroid test panel. This consists of five simple blood tests: TSH, free T4, free T3, reverse T3, and two types of thyroid antibody levels called anti-TPO and anti-thyroglobulin. 

Most women will have had their TSH levels tested at some point in their evaluation, but this number alone can miss many cases of Hashimoto's. That's because thyroid function is very erratic (or up and down) in the early stages of this condition—so TSH levels may actually be normal at the time of your test, even if thyroid function is compromised. This test can also miss cases of peripheral hypothyroidism, where the body is not creating enough active thyroid hormone (ft3) but has normal levels of TSH and T4. A full thyroid test panel, on the other hand, will identify these issues as early as possible, making it more likely that you'll be able to manage them with lifestyle changes alone.

Our thyroids are only one part of a bigger interconnected endocrine system in which all of our hormones communicate with each other and try to maintain balance. So, how well thyroid hormone treatment works, should you need it, is dependent on getting your other hormones balanced, including insulin (which regulates blood sugar) and adrenal hormones (which govern your fight-or-flight response). The conventional medical system likes to focus on just one part of the body at a time, but when it comes to the fertility-thyroid connection, you have to zoom out and look at the body as a whole.

Working on improving gut health with dietary changes and eating in a way that calms down autoimmunity and keeps blood sugar stable should also be integral parts of a treatment plan to restore thyroid health. Many of my patients have been successful in improving their thyroid function and fertility with elimination diets, which often involve avoiding gluten, soy, dairy, processed sugar, and alcohol and instead focusing on eating a more organic, minimally processed, whole-foods-based diet. Helping the body get out of fight-or-flight mode with regular sleep, exercise, and working to reduce stress with acupuncture, yoga, and meditation can also promote healthy thyroid functioning.