Category: Women's Health
Thyroid and Menstruation: How Your Thyroid Affects Your Cycle
The thyroid plays an important role in your hormonal balance and can affect your menstrual cycle. Both an underactive and an overactive thyroid can cause irregular, heavy, or even absent periods. By testing your thyroid levels, you’ll gain insight and be able to work more effectively toward restoring your cycle and energy levels.
Has your cycle suddenly become irregular, are you bleeding much more than before, or has your period stopped? If so, your first thought is probably estrogen and progesterone. But your thyroid could also be the cause. A thyroid that’s underactive or overactive can seriously disrupt your menstrual cycle.
In this blog, you’ll learn how your thyroid and your menstrual cycle are connected, what signs to look for, and which blood tests you can get.
How are your thyroid and your menstrual cycle related?
Your thyroid gland is located at the base of your neck and produces the hormones T4 and T3. These hormones determine how quickly your body uses energy. They affect your heart rate, body temperature, digestive system, and your ovaries.
The pituitary gland in your brain regulates the thyroid gland with TSH. If your thyroid gland produces too little hormone, your TSH level rises. If it produces too much, your TSH level drops. These fluctuations affect the hormones that regulate your ovulation and menstruation. That’s why you sometimes first notice a thyroid problem through changes in your cycle.
Hypothyroidism and Menstruation
Many women with an underactive thyroid (hypothyroidism) experience heavier or longer periods. Your cycle may also become irregular, and sometimes ovulation may not occur. This can make it more difficult to get pregnant.
An underactive thyroid can also cause your prolactin levels to rise. Prolactin is the hormone that also regulates milk production. If your prolactin levels are too high, you may miss a period or experience some discharge from your nipples even though you’re not pregnant. You can read more about this in our blog post on prolactin.
A common cause of an underactive thyroid is Hashimoto’s disease. This is an autoimmune disease that is more common in women. Read more in our blog about Hashimoto’s disease.
Overactive Thyroid and Menstruation
If your thyroid is overactive (hyperthyroidism), the opposite often happens. Your periods become lighter, shorter, or less frequent. For some women, they stop altogether.
An overactive thyroid also often causes symptoms such as heart palpitations, restlessness, sweating, and weight loss without eating less.
Is your period late? Your thyroid might be a factor
A missed period often has another cause. These can include pregnancy, stress, significant weight loss, intense exercise, PCOS, birth control pills, or the onset of menopause. However, both an underactive and an overactive thyroid can also cause it. If, in addition to a missed period, you’re experiencing other symptoms listed in the table below, it’s a good idea to have your thyroid tested.
Signs of an Underactive Thyroid
| Slow thyroid | Overactive Thyroid |
|---|---|
| Heavier or longer periods | Lighter or Shorter Periods |
| Irregular cycle | Periods occur less frequently or stop altogether |
| Tired and low on energy | Restless and agitated |
| Gaining Weight Without Eating More | Lose Weight Without Eating Less |
| Feeling cold easily, cold hands and feet | Gets hot quickly, sweats a lot |
| Dry skin and thinner hair | Palpitations |
| Constipation | Going to the bathroom more often |
Please keep in mind that many of these symptoms can also have other causes. A blood test will provide more clarity.
Which blood tests should you get?
TSH and free T4 levels show whether your thyroid is underactive or overactive. Free T3 provides a more complete picture, especially if you suspect an overactive thyroid. You can have all three tested together with the Thyroid Test (TSH, free T4, and FT3).
Want to know if Hashimoto’s is the cause? Then have your anti-TPO levels tested as well. These are antibodies against your own thyroid gland.
Since your cycle is also regulated by other hormones, you can also consider these levels:
- Prolactin, if your period is late or you’re leaking fluid from your nipples.
- Ferritin and hemoglobin when you lose a lot of blood. Heavy periods can quickly deplete your iron stores. Be sure to read our blog about heavy periods and iron deficiency.
- Your female hormones, such as estradiol, LH, and FSH. Check out our hormone tests for women.
What can you do yourself?
Track your cycle for a few months using an app or calendar. Note the length of your cycle, the amount of bleeding, and any symptoms you experience. This will help you identify patterns and give you concrete information to discuss when reviewing your test results.
Your thyroid needs iodine and selenium. You can usually get enough of these from your regular diet, for example, through bread made with iodized salt, fish, eggs, and dairy products. Don’t just take extra iodine or selenium without consulting a doctor, because too much can actually disrupt your thyroid function.
Have your blood tested if you recognize any of these symptoms. If your results are abnormal, our medical team will call you first. You can also book a consultation with our lifestyle doctor to discuss your results and symptoms together.
When should you see your doctor?
See your doctor if your period hasn’t come for more than three months and you’re not pregnant, if you’re bleeding so heavily that it’s affecting your daily life, or if you’re trying to get pregnant and your cycle is irregular. If your thyroid test results are abnormal, discuss with your primary care physician whether further testing or treatment is necessary.
The Interplay with Pregnancy and Menopause
It also works the other way around. During pregnancy and after childbirth, your thyroid has to work extra hard. During menopause, thyroid symptoms and menopausal symptoms are very similar. Not sure which one it is? Then read our blog about menopausal symptoms or the thyroid.
Conclusion
Your thyroid and your menstrual cycle are closely linked. An underactive thyroid often causes heavier or irregular periods. Conversely, an overactive thyroid can result in lighter periods or missed periods. Do you recognize the signs? With a blood test for TSH, free T4, and free T3, you can quickly determine whether your thyroid is a factor.
Frequently Asked Questions About the Thyroid and Menstruation
Can an underactive thyroid affect your menstrual cycle?
Yes. With an underactive thyroid, your periods often become heavier or last longer, and your cycle may become irregular.
Can your thyroid cause your period to stop?
Yes, this can happen with both an underactive and an overactive thyroid. There are also many other causes, so get it checked out if your period is late for an extended period.
Do I need to fast before a thyroid test?
No, you don’t need to fast for the TSH, free T4, and free T3 tests.
Will my cycle return to normal once my thyroid is treated?
Often, yes. Once your thyroid levels are back to normal, many women’s menstrual cycles return to normal. If your cycle remains irregular, discuss this with your doctor.
Resources
- Dutch College of General Practitioners (NHG). NHG Standard for Thyroid Disorders.
https://richtlijnen.nhg.org/standaarden/schildklieraandoeningen
Medical disclaimer: This information is general in nature and is not intended to replace personal medical advice, diagnosis, or treatment. If you have any symptoms, receive an abnormal test result, or have any concerns, please contact your primary care physician or treating physician.
Have a question about your results?
Leave a comment. Our specialists are happy to help you.
Want to know right away?
View the recommended test(s):
