How Your Thyroid Affects Your Menstrual Period

by Mary Shomon Patient Advocate

Many women don't realize menstrual problems can be a symptom of an undiagnosed thyroid condition. At the same time, if you are a woman with thyroid disease, you may not realize that inadequate treatment of your thyroid condition may also affect your menstrual periods.

Your thyroid is a small, butterfly-shaped gland, located in your neck, that helps oxygen and energy reach your cells, organs, and tissues. When you don’t have enough thyroid hormone, that is referred to as hypothyroidism, which is the more common thyroid condition. When you have too much thyroid hormone, that’s hyperthyroidism. Women are as much as ten times more like to experience thyroid conditions versus men.

All your body’s key processes — including your menstrual cycle — rely on a healthy thyroid for proper functioning.

Thyroid issues, when undiagnosed or not optimally treated, can affect your menstrual cycle. Let’s take a look at the menstrual changes that may result from thyroid issues.

Hypothyroidism and your menstrual periods

Undiagnosed or improperly managed hypothyroidism is associated with a variety of menstrual irregularities.

  • Early menstruation: The average age of menarche (the first period) is around 12 in the U.S. Hypothyroidism in young girls can trigger an unusually early start of menstruation, before the age of 10, for example. This early puberty is known as "precocious puberty."

  • Heavy menstrual periods: Very heavy periods, called "menorrhagia," are linked to hypothyroidism. Menorrhagia is defined as excessively heavy or prolonged menstrual bleeding, such as soaking through a sanitary pad every hour for several hours or more.

  • More frequent menstrual periods: Hypothyroidism is known to cause periods to come more frequently, a condition known as polymenorrhea. You may find that your period comes every 21 days, for example, instead of the average 28-day cycle.

  • Longer menstrual periods: While a typical menstrual period lasts five days on average, hypothyroidism may make your cycle longer, lasting six days or longer.

  • Painful menstrual periods: Painful menstrual periods are known as dysmenorrhea. Dysmenorrhea pain may include backaches, cramps, headaches, and stomachaches, among other symptoms.

Hyperthyroidism and menstrual periods

Undiagnosed or improperly managed hyperthyroidism is associated with a variety of menstrual irregularities.

Late menstruation/delayed puberty: Hyperthyroidism is associated with a delayed start of puberty in some teenage girls, who may not have their first period until age 15 or older.

  • Lighter menstrual periods: Periods can be lighter than usual.

  • Shorter menstrual periods: Periods may be shorter than the average five days.

  • Sporadic menstrual periods: Periods may be sporadic, skipping a month or two, then resuming, or come every 35 or 40 days, for example. This is called oligomenorrhea.

  • Absent menstrual periods: Hyperthyroidism can cause you to stop menstruating entirely for extended periods of time. The lack of periods is called amenorrhea.

Thyroid disease, menstruation, and your fertility

Thyroid disease is also associated with two conditions that can affect your fertility. One is anovulation, the failure to release an egg. When no egg is released, you are unable to become pregnant during that cycle.

Hypothyroidism may also trigger a condition known as “short luteal phase.” Your luteal phase is the time between ovulation — release of an egg — and the start of your period. In order to have a successful pregnancy, you need a luteal phase of around 14 days to allow a fertilized egg enough time to successfully implant and start to develop. If your luteal phase is too short, a fertilized egg may end up being expelled during your menstrual period, stopping a pregnancy from continuing.

When to see your practitioner

If you are being treated with thyroid hormone replacement drugs, be sure that you are optimally treated, as symptoms such as menstrual problems may persist if you are not at the optimal thyroid levels, or on the proper thyroid drug for you.

If you are hyperthyroid and taking antithyroid drugs, find out your TSH level, as too low a TSH level may be triggering menstrual-related symptoms.

You should see your practitioner:

  • If you are being treated for a thyroid condition, but still have a menstrual irregularity

  • If you have heavy menstrual bleeding that lasts for more than 24 hours

  • If your menstrual period regularly lasts more than 7 days

  • If your menstrual periods come every 21 days or less

  • If your periods have stopped for more than three months and you are not pregnant

  • If you have a significant increase in menstrual pain

Mary Shomon
Meet Our Writer
Mary Shomon

Mary Shomon is a patient advocate and New York Times bestselling author who empowers readers with information on thyroid and autoimmune disease, diabetes, weight loss and hormonal health from an integrative perspective. Mary has been a leading force advocating for more effective, patient-centered hormonal healthcare. Mary also co-stars in PBS’ Healthy Hormones TV series. Mary also serves on HealthCentral’s Health Advocates Advisory Board.