Do-Eun Lee, MD, has been practicing medicine for more than 20 years, and specializes in diabetes, thyroid issues and general endocrinology. She currently has a private practice in Lafayette, CA. 

Thyroid problems can result in menstrual irregularities. This is because the thyroid gland, a small butterfly-shaped gland located at the base of the front of your neck, plays an essential role in your reproductive health.

The thyroid directly affects your ovaries and indirectly interacts with sex hormone-binding globulin (SHBG). SHBG is a protein that "sticks" to reproductive hormones so they can be carried throughout your body.

Menstrual problems tend to be most common in those with severe thyroid disease and less common in those with more mild or moderate cases.

If you are experiencing unusual menstrual symptoms, it's worth asking your healthcare provider to evaluate your thyroid.

This article explains why thyroid disorders can cause menstrual irregularities. It also covers some of the most common menstrual symptoms related to thyroid disorders, plus what you can do about them.

Problems with your menstrual cycle may be due to an underactive or overactive thyroid. How symptoms present could depend on which type of thyroid disorder you have.

Hypothyroidism, or an underactive thyroid gland, occurs when the body produces too little thyroid hormone. There are several menstrual problems associated with hypothyroidism, including:

The first-line treatment for hypothyroidism is the thyroid hormone replacement medication Levoxyl (levothyroxine ). This medication has been shown to improve menstrual problems even in people with normal thyroid function. That said, some people who use thyroid medication continue to experience abnormal periods.

Hyperthyroidism is a disorder of an overactive thyroid gland. That means your body produces too much thyroid hormone.

Menstrual abnormalities seen with hyperthyroidism include:

Treatment with an antithyroid drug can help prevent menstrual and fertility problems.

Another option is radioactive iodine (RAI) therapy, which shrinks the thyroid. However, this treatment is not safe during pregnancy.

Too little thyroid hormone can cause heavy menstrual bleeding, while too much thyroid hormone can have the opposite effect. Both thyroid conditions can cause missed or no periods and affect fertility.

The American College of Obstetricians and Gynecologists (ACOG) defines heavy menstrual bleeding as one or more of the following:

Keep in mind, while hypothyroidism is one potential cause of heavy bleeding, there are many other possible causes, including:

Be sure to see your OB/GYN if you are experiencing heavy periods. To help with diagnosis, they may want to perform some tests such as a:

Hypothyroidism and some other medical conditions can cause heavy periods. To determine the cause, your doctor may need to do a pelvic exam, ultrasound, and bloodwork.

Hypothyroidism and hyperthyroidism can also lead to absent periods (amenorrhea) or infrequent periods (oligomenorrhea). Irregular periods are more common.

Absent or infrequent cycles can occur from high thyroid releasing hormone (TRH) in people with hypothyroidism. The high TRH levels trigger the pituitary gland (a pea-sized organ located at the base of the brain) to release prolactin. In people with hyperthyroidism, too much thyroid hormone leads to increased SHBG, which can prevent ovulation.

Too much prolactin interferes with the ability of the ovaries to produce estrogen. Reduced estrogen can lead to some reproductive health symptoms and issues, including:

Thyroid problems can cause your period to stop altogether or to occur infrequently. This is true for people with both hypothyroidism and hyperthyroidism.

Since a lack of thyroid hormone can prevent ovulation, having thyroid problems can make it difficult to get pregnant. Hyperthyroidism may also cause early menopause, or menopause that occurs before or just after the age of 40.

Moreover, people with hypothyroidism or hyperthyroidism who are pregnant have an increased risk of miscarrying.

For people with hypothyroidism, treatment with (levothyroxine ) may improve fertility and lower the risk of pregnancy loss.

People with hyperthyroidism are often treated with antithyroid medication during the second half of pregnancy. Because these medications cross the placenta, however, their use needs to be carefully monitored by a healthcare provider.

Thyroid conditions can have an impact on your menstrual cycles. Symptoms may range from heavy and frequent periods to irregular and absent cycles. These symptoms are due to how thyroid hormones impact reproductive hormone production.

As such, menstrual irregularities could also affect fertility and pregnancy.

While a change in your menstrual cycle may be the first indication of a thyroid disorder, remember that there are many other potential causes. It's always best to contact your healthcare provider for an evaluation so the underlying cause can be confirmed.

Gude D. Thyroid and its indispensability in fertility. J Hum Reprod Sci. 2011 Jan-Ape;4(1):59-60. doi:10.4103/0974-1208.82368 

Kakuno Y, Amino N, Kanoh M, Kawai M, Fujiwara M, Kimura M, et al. Menstrual disturbances ijn various thyroid diseases. Endocr J. 2010;57(12):1017-22. doi:10.1507/endocrj.K10E-216

Vissenberg R, Van den Boogaard E, Van Wely M, et al. Treatment of thyroid disorders before conception and in early pregnancy: a systematic review. Hum Reprod Update. 2012;18(4):360-73.

Jamilian M, Talaei A, Chehrei A, Rezvanfar MR, Rafei F. The study of the effect of levothyroxine on dysfunctional uterine bleeding (DUB) in euthyroid women. ISMJ. 2017;20(4):317-25.

Saran S, Gupta BS, Philip R, Singh KS, Bende SA, Agroiva P, et al. Effect of hypothyroidism on female reproductive hormones. Indian J Endocrinol Metab. 2016 Jan-Feb; 20(1):108-13. doi:10.4103/2230-8210.172245

American College of Obstetricians and Gynecologists. Frequently asked questions. Gynecologic problems. Heavy menstrual bleeding.

Johns Hopkins Medicine. Thyroid disorders in women.

Andersen SL, Laurberg P. Managing hyperthyroidism in pregnancy: current perspectives. Int J Womens Health. 2016;8:497-504. doi:10.2147/IJWH.S100987 doi:10.2147%2FIJWH.S100987

By Mary Shomon Mary Shomon is a writer and hormonal health and thyroid advocate. She is the author of "The Thyroid Diet Revolution."

Thank you, {{form.email}}, for signing up.

There was an error. Please try again.