How Your Thyroid Affects Your Menstrual Cycle

Key points:

  • The thyroid affects your menstrual cycle health.
  • Thyroid dysfunction be associated with light, heavy, or irregular periods, PMS, or skipped ovulation or skipped periods.
  • Thyroid problems are also associated with infertility, miscarriage, PCOS, endometriosis, and ovarian cysts.
  • There are steps you can take to support thyroid health, including dietary and lifestyle habits, that can in turn improve your menstrual cycle ease and regularity, as well as ovulation and fertility.

Read or listen to How Your Thyroid Affects Your Menstrual Cycle.


Heavy periods. Skipped ovulation. Irregular Periods. Breast tenderness. PMS. Ovarian Cysts. Fertility challenges. Endometriosis. PCOS.

What do all of these have in common?

Well, aside from affecting a combined 1 in 3 women, they may also be tied to a thyroid problem particularly hypothyroidism, a slow functioning thyroid, or hyperthyroidism, when your thyroid goes into hyper-drive.

In this article and podcast, I teach you all about T4 and T3 and how the function or dysfunction of your thyroid can be a  factor in the function or dysfunction of your periods, including whether they are regular, how long, heavy, whether you skip them, and whether you’re ovulating -and how PCOS, ovarian cysts, and more factor in.

Meet Your Thyroid

When we think of our periods and menstrual cycles, we tend to think of ‘the leading ladies’” estrogen and progesterone. But other hormones, like thyroxine (T4) and triiodothyronine (T3), are playing a major role behind the scenes. While these names might not roll off the tongue as easily, they play a pivotal role in your menstrual cycles including whether they are regular, how long, heavy, whether you skip them, and whether you’re ovulating.

You may have guessed by their names that the aforementioned hormones, T4 and T3, are produced in your thyroid. Your thyroid is a butterfly-shaped gland in the lower front part of the neck. In fact, while both of these are produced there, T4 is produced most abundantly, and is then converted to T3 – the more active form – in the liver.

T3 then travels to cells throughout your body and does all of the thyroid’s heavy lifting. It acts as your body’s thermostat, turning the dial up or down on your body’s energy expenditure and metabolism, growth, and reproductive functions and is involved in hundreds (or more) biological functions including brain development and function, breathing and heart rate, nervous system functions, body temperature, muscle strength, skin health, and mood, weight, and cholesterol levels.

It also plays a major role in your menstrual cycle. And when your thyroid function is off, it can cause a host of cycle symptoms and imbalances.

Hypothyroidism and Hyperthyroidism

The two most common types of thyroid problems are hypothyroidism, in which the thyroid is under functioning, and hyperthyroidism, in which it over functions. Hashimoto’s is an autoimmune form of hypothyroidism, while Grave’s disease is an autoimmune form of hyperthyroidism.

It’s estimated that 1 in 8 women have hypothyroidism. Symptoms, in addition to heavy, skipped, or excessively light periods, can include:

  • Feeling sluggish, tired, or having zero energy
  • Gaining weight in the past few months without being able to pinpoint why
  • Trouble losing weight, no matter how hard you try
  • Experiencing insomnia, trouble falling asleep, or waking up in the middle of the night
  • Brain fog, memory problems, or trouble concentrating
  • Feeling sad or depressed and not being able to pinpoint why
  • Feeling anxious or worried, but not able to pinpoint why
  • Slugging bowels or constipation
  • Feeling chilly or cold – even when everyone else is warm
  • Having dry, itchy, or rough skin
  • Having dry, course, or brittle hair and nails
  • Thinning hair or hair loss
  • Thinning outer third of eyebrows
  • High cholesterol
  • Puffy face and around your eyes
  • Fertility problems
  • Postpartum depression or trouble producing breast milk

Hyperthyroidism is much less common, affecting an estimated one in 100 women . Symptoms, in addition to menstrual cycle ones,  can include:

  • Nervousness, irritability, mood swings
  • Muscle weakness
  • Heat intolerance, feeling overheated
  • Trouble sleeping
  • Weight loss
  • Tremor, usually in the hands
  • Rapid, irregular heartbeat
  • Frequent bowel movements, loose stools
  • Fatigue (usually from inability to sleep)

How Your Thyroid Affects Your Menstrual Cycle

Both hyperthyroidism and hypothyroidism can affect your menstrual cycle. According to at least one study, the more severe your thyroid problem, the more severe your menstrual symptoms are likely to be. In one study, women with severe hypothyroidism had 3 times the frequency of menstrual problems compared to women with mild hypothyroidism.

Heavy Periods. Not sure whether your period is “heavy?” Here are the clues: a period lasting longer than 7 days, soaking through a pad or tampon every hour for several hours in a row, needing to wear more than one pad at a time, having menstrual blood clots the size of a quarter or bigger – those are all signs that what you’re experiencing falls into the heavy category.

Absent or Infrequent Menses: In hyperthyroidism, high levels of thyroid releasing hormone (TRH) trigger the release of prolactin by the pituitary gland (a pea-sized organ located at the base of the brain). Prolactin interferes with the production of estrogen from the ovaries, causing infrequent or absent periods, and can be a cause of infertility as well. Hypothyroidism is more likely to be associated with PCOS, discussed below, causing heavy menstrual bleeding.

Skipped Ovulation:  Since thyroid disorders can lead to menstrual cycle disruption, this of course is going to affect fertility. This is why, not surprisingly, both hypothyroidism and hyperthyroidism have been linked to infertility. In one study, 76 percent of women with hypothyroidism were able to conceive after being treated for their thyroid condition. Some of my patients don’t even realize they have a thyroid dysfunction until they have difficulty getting pregnant. Often, a diagnosis comes as a relief because it’s the first step toward getting to the root of the problem, and once a thyroid disorder is addressed, it can become easier to conceive. Hypothyroidism and hyperthyroidism both also increase miscarriage risk, making proper treatment all the more important.

Cyclic Breast Tenderness is another symptom that sometimes accompanies hypothyroidism and affects the menstrual cycle.

Your Mood and Your cycle: A slow functioning thyroid is linked to fatigue, anxiety, and depression. In fact, the cause of depression in 15 percent of women on antidepressants is an undetected thyroid problem. This may be a contributing factor to PMS in some women, and should be considered.

In addition to all of these direct impacts on your menstrual cycle, the thyroid can also play a role in conditions including polycystic ovary syndrome (PCOS), ovarian cysts, and endometriosis, which also affect your cycle.

PCOS: In recent years, a number of studies have found a connection between an increased rate of thyroid disorder in women with PCOS. An underactive thyroid causes an increase in testosterone, follicle stimulating hormone (FSH), and luteinizing hormone (LH) levels, all of which can cause irregular and skipped periods, as well as heavier periods when Aunt Flo does arrive.  Further, as many as a third of women diagnosed with PCOS test positive for the presence of anti-thyroid antibodies. So if you have PCOS, thyroid health absolutely is going to be a big part of the conversation with your doctor.

Ovarian cysts: When the thyroid is underactive, the pituitary gland tries to make up for it by releasing more of a hormone called prolactin. Too much prolactin can actually suppress ovulation, and at the same time increases the production of follicle-stimulating hormone (FSH). This means that your ovaries are getting the message to produce a lot of follicles, but they don’t end up fully maturing. This can lead to recurrent – and often very painful – ovarian cysts. Signs of an ovarian cyst include swelling, bloating, or pain in the lower abdomen. The pain may be sharp or come and go, but either way it’s certainly not pleasant. So before you have that surgery (unless it’s an emergency, then please by all means, do), consider having your thyroid levels tested (see below).

Endometriosis: Endometriosis, in turn, can be a source of irregular periods and terrible period pain; menstrual migraines are also more common in women with endometriosis.  There’s also a link between thyroid disorders and endometriosis. Researchers have found that women with endometriosis had increased levels of T4 hormones and decreased levels of T3 hormones. In one study, compared with published rates in the general US female population, women with endometriosis were 9.6 times more likely to be diagnosed with hypothyroidism. In particular, Hashimoto's thyroiditis was 6.5 times more common in women with endometriosis.

5 Things You Can Do Now to Take Control of Your Thyroid Health

Get tested – and treated if needed.

My motto with thyroid problems is ‘test, don’t guess.' If you suspect a thyroid problem, can’t seem to figure out what’s throwing your menstrual cycle off, or have PCOS, endometriosis, or recurrent ovarian cysts, see your primary care provider for a proper thyroid diagnosis to see if a thyroid problem figures in. Unfortunately most doctors don’t routinely check a full panel of thyroid tests, so they end up missing a thyroid diagnosis – leading millions of women without answers and suffering symptoms and health consequences. Here’s what I order in a complete thyroid panel, and what you can ask your doctor to do for you. It can really make a difference in your hormone health.

If you do have a thyroid problem, getting proper treatment can make a huge difference in getting your cycles back on track. In one study, 7 out of 10 women with untreated hypothyroidism were found to have irregular menstrual cycles; once treated, 50% of the women experienced regular cycles. While natural approaches and nutritional and herbal supplements may help improve your thyroid health, thyroid hormone is essential to your overall hormone health and much more, and thyroid hormone medication may be essential. Test your thyroid function to find out what is going to the best starting place for you personally.

Take care of your adrenal health.

When you’re under prolonged chronic stress, your adrenal system tells your body to conserve rather than expend energy. Your thyroid slows down, too. Even if you produce enough active thyroid hormone, cortisol blocks your body from activating it and letting your cells use it. It’s like a warning system that protects you from overusing precious energy reserves. In a next-level effort to prevent you from expending energy, your thyroid puts a lid on your ovarian function, because ovulation is a very energy intensive process. It’s one of the main ways that the thyroid-hormone connections get activated.

Stress also uses up important nutrients you need for thyroid health, like magnesium, so you get a double whammy – and it’s also doubly important to make sure you’re getting the nutrients you need! Ashwagandha is an adaptogen that has been shown to increase active thyroid hormone levels, and also reduces cortisol – a win-win in stress-related thyroid problems. A proper dosage is 2,000 milligrams daily; it’s safe while breastfeeding, but not in pregnancy, and not for you if you have hyperthyroidism.

Support healthy estrogen levels.

Estrogen plays a role in how well the thyroid is functioning. Not surprisingly, therefore, thyroid disorders are most common in women between puberty and menopause. Elevated estrogen levels lead to an increase of thyroid binding globulin (TBG), which binds circulating thyroid hormone, making it unable to do its job, and giving you symptoms of a slow functioning thyroid even when your thyroid is perfectly healthy (this is important because it might also be missed on thyroid tests unless TBG and SHBG are checked). Elevated estrogen levels, sometimes called estrogen dominance, can be due to endocrine disruptors from the environment, estrogen in birth control or other medications, or from your own hormone imbalances due to slow breakdown of estrogen in the liver, or difficulty eliminating it due to disruptions in your gut microbiome or even chronic constipation. To address each of these factors – avoid plastics in food packaging, eat organic, go clean and green with your cosmetics, and support healthy gut flora with 2 Tbsp. ground flaxseed in your food daily, lactofermented foods in your diet, a daily probiotic, and Vitamin B6 50 mg/day.

Make sure you’re getting your thyroid-healthy nutrients.

For some women, a low-carb diet or low-blood sugar triggers the brain’s “danger signals,” and may lower the thyroid’s production of T3 because your body thinks it’s in energy conservation mode. Make sure your diet is rich in the below nutrients, which can include taking a supplement, if needed.

  • Iodine: This nutrient is essential for thyroid hormone production, just one of its many roles. Many tissues need it, including the brain, immune system, ovaries, uterus, and breasts. In fact, the ovaries contain more iodine than any other organ except the thyroid.
  • Vitamin D: Technically a hormone, vitamin D3 receptors can be found in the uterus and ovaries, and is important for healthy thyroid function.  Vitamin D levels tend to be lower in people with hypothyroidism. It’s important to have optimal blood levels of between 50-80 ng/mL. In some cases, vitamin D is the missing link when a woman is already on supplemental thyroid hormones, but her dose needs to keep changing or she’s not seeing results. Before starting vitamin D as a thyroid supplement it’s optimal to have your levels tested, but if for some reason you’re unable to, a standard dose of 2,000 units/day is appropriate for most adults. Vitamin D supplements are safe during pregnancy and breastfeeding.
  • Selenium: The body turns the mineral selenium into the powerful antioxidant glutathione, which protects the thyroid from inflammation and can reduce thyroid attacking antibodies. Selenium is also critical in forming the active form of thyroid hormone, free T3 (FT3) from T4. A note of caution: selenium can worsen thyroid function if you’re also experiencing iodine deficiency. In terms of a dosage, aim for 200 mcg/day and do not exceed that amount. Selenium supplements are safe during pregnancy and while breastfeeding.
  • Zinc: Zinc is an important nutrient for nourishing your thyroid and converting T4 to T3 so you produce enough active thyroid hormone. It may also improve stress-related thyroid problems. Take 30 mg/day and take this supplement with meals to prevent nausea. Zinc is safe when pregnant and breastfeeding.
  • Magnesium: This nutrient is a cofactor in hormone production, meaning without magnesium you can’t make estrogen, progesterone, thyroid hormone, and others. Aim to get 400 mg/day.

Keep in mind, too, that being on the Pill depletes some of these nutrients – and others. As the Pill has other risks, you can consider another birth control option (or another way to manage hormonal symptoms if you're on the Pill for a hormone imbalance) and replete the nutrients that may have gotten robbed by this medication. You can learn which ones here.

Support liver health.

The liver plays a role in the chemical process that develops and metabolizes estrogen, called metabolic detoxification. In this podcast I teach you which foods to eat to support healthy, natural hormone detoxification, and here I talk about the herbs and nutrients you can use if extra help is needed. Additionally, the nutrients I mentioned above support the liver's job in converting inactive to active thyroid hormone.

Be Part of the Revolution

I hope this article gives you deeper insight into the importance of thyroid health for menstrual cycle health, the confidence that you can get the thyroid answers you need from proper testing, and the tools to get started on rebalancing your cycle by taking care of your thyroid. Taking care of our health and getting the answers we might not always get from our doctors is a revolutionary act!

Want to take a deeper dive into thyroid health? Grab your copy of my book, The Adrenal Thyroid Revolution where you'll also learn how thyroid affects libido, menopause, and much more, and you'll find a complete 5 step pathway to the foods, nutrients, gut, liver, and adrenal support for your thyroid health, as well as more on testing and best thyroid medications.

See links in the article.