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Hypothyroidism and Your Period

Your menstrual cycle may be a window into your thyroid and overall health.
Hypothyroidism and Your Period
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In this article:

  • How does hypothyroidism affect your menstrual cycle?
  • What are the characteristics of a regular menstrual cycle?
  • What about irregular periods?
  • How to treat irregular periods caused by hypothyroidism

How does hypothyroidism affect your menstrual cycle?

Hypothyroidism is a condition where the thyroid gland produces too little thyroid hormone. The thyroid is the body's metabolic powerhouse because it drives processes like blood pressure, heart rate, temperature, and tissue development. When your body does not produce enough thyroid hormone, it can cause your metabolic processes to change and slow down. Along with feelings of depression, fatigue, dry skin, weight gain, and cold intolerance, women can experience irregular menstrual periods as a symptom of hypothyroidism

Endocrine glands produce hormones that affect every organ system in your body. When one endocrine gland is not functioning correctly, it can throw off your whole system. Your reproductive system is driven primarily by communication between your hypothalamus, pituitary gland, and ovaries. However, thyroid hormones also play a role in your reproductive system by helping regulate your metabolic rate.

TSH and prolactin

Too little thyroid hormone causes your pituitary gland to release more thyroid-stimulating hormone (TSH) and prolactin. Usually referred to as the milk hormone (and rightly so as it stimulates breast milk production), prolactin also plays a role in supporting ovulation. When prolactin levels increase, it can interfere with your ovaries producing estrogen and progesterone, which can inhibit ovulation and cause you to skip your period. You can measure your prolactin levels with an at-home female hormone blood test.

Estrogen and progesterone

Estrogen is the primary female sex hormone that is responsible (among many things) for controlling the growth of the uterine lining in the first half of the menstrual cycle until you ovulate. Ovulation is where your ovaries release an egg for fertilization. When an egg is released, it leaves behind a sack (called the follicle) that produces progesterone. This hormone is essential for stabilizing the uterine lining so that an egg may implant if it becomes fertilized. It also balances the estrogen levels, as too much estrogen or not enough progesterone can lead to heavy bleeding. Thus, while we usually assume that periods are a sign that we are ovulating, we can still have periods without ovulation, and these periods tend to be heavier. 

What are the characteristics of a regular menstrual cycle?

The term "regular" really isn't applicable, as every woman has a different version of what is "normal" for her. However, most women have the following characteristics associated with their period:

  • A period that lasts between 4-7 days, with a period cycle lasting between 26-32 days.
  • Blood that is usually bright red and often becomes browner as you near the end of your period. Typically, the blood can be dense or stringy, as you also lose uterine tissue in your menstrual blood. Heavy clots should not accompany bleeding. 
  • Slight abdominal discomfort that may include mild to moderate cramping.

A regular period should be one that is consistent. Whether your periods last four days or seven days, it should be about the same each time. Suppose your period is not consistent or does not have the characteristics mentioned above. In that case, it is worth consulting your doctor to see if something is amiss with your endocrine system.

What about irregular periods?

Changes in the length, flow, and color of your periods indicate that you have some form of a disturbance that is interfering with your normal menstrual cycle. Some women may even not have periods unrelated to pregnancy or may experience spotting in between periods. Moderate to severe symptoms of pre-menstrual syndrome (PMS) can also be a sign that your hormones are out of balance.

As we have discussed, hypothyroidism can cause irregular periods. Other causes of irregular periods include:

  • Hyperthyroidism (overactive thyroid)
  • Hormonal birth control such as pills and intrauterine devices (IUDs)
  • Too much exercise
  • Stress
  • Perimenopause
  • Uterine polyps or fibroids

While the cause may not be apparent, an irregular period is your body trying to send you a blatant message that something is disrupting your system. Meet with your doctor to get to the bottom of what is causing irregularity in your menstrual cycle.

How to treat irregular periods caused by hypothyroidism

Suppose hypothyroidism is the suspected culprit behind irregular periods. In that case, your doctor will order a blood test to look at your thyroid function. You will likely see results for thyroid-stimulating hormone (TSH), free T3, free T4, and TPO antibodies on your blood work. These labs help your doctor get a full picture of how your thyroid is working overall. 

Typically, high TSH and low T4 is cause for a hypothyroidism diagnosis. TPO antibodies may or may not be present. If they are, it indicates that an autoimmune condition called Hashimoto's is causing your hypothyroidism. 

Optimizing your thyroid hormone levels with thyroid hormone replacement medication is the first step towards restoring normalcy to your periods. It can take some time and adjustment of your medication dose to find the perfect dose for you. Lifestyle modifications, such as diet and exercise, can also significantly improve your hypothyroid symptoms and overall health. 


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Julia Walker, RN, BSN

Clinical Nurse

Julia Walker, RN, BSN, is a clinical nurse specializing in helping patients with thyroid disorders. She holds a Bachelor of Science in Nursing from Regis University in Denver and a Bachelor of Arts in the History of Medicine from the University of Colorado-Boulder. She believes managing chronic illnesses requires a balance of medical interventions and lifestyle adjustments. Her background includes caring for patients in women’s health, critical care, pediatrics, allergy, and immunology.

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