Healthcare provider using chart to explain whether thyroid medication affects the menstrual cycle

Does Thyroid Medication Affect the Menstrual Cycle?

Medically reviewed on July 14, 2023 by Jordan Stachel, M.S., RDN, CPT. To give you technically accurate, evidence-based information, content published on the Everlywell blog is reviewed by credentialed professionals with expertise in medical and bioscience fields.

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It’s common for people with female anatomies to develop thyroid disease as a result of hormonal imbalances caused by menopause, puberty, or pregnancy. [1] In fact, women and people assigned female at birth (AFAB) are more likely to develop thyroid issues during their lifetime, compared to people with male anatomies, for this reason. [2]

These hormonal changes can, unfortunately, impact the menstrual cycle, in addition to mood, weight, and temperature control. [3] Fortunately, healthcare providers can prescribe medication to restore balance to optimize your thyroid function. That said, does thyroid medication affect the menstrual cycle, too?

The short answer is that it can—typically by restoring hormone levels to regulate menstruation and ovulation.

How Do Thyroid Issues Impact the Menstruation Cycle?

The thyroid is a gland found in the neck. It releases hormones that regulate various functions of the endocrine system. Primarily, it controls metabolism and energy use, but it serves additional purposes, too.

Since the endocrine system is made up of various organs and glands—including the hypothalamus, pituitary gland, heart, pancreas, kidneys, ovaries, and testes—it significantly impacts the whole body. [4]

More specifically, the thyroid plays a role in the regulation of [4]:

  • Heart rate
  • Breathing
  • Digestion
  • Body temperature
  • Brain, skin, and bone development and maintenance
  • Cognitive agility
  • Fertility

A thyroid condition can lead to an irregular menstrual cycle due to the hormone imbalance that often coincides. Part of this menstrual irregularity is due to the impact of a thyroid problem on fertility and reproductive health.

Effects of a Thyroid Disorder on Fertility

Let’s take a look at thyroid and fertility. The thyroid helps to initiate ovulation—the process of releasing an egg from the ovaries, which allows the egg to mature and travel through the fallopian tubes and can become fertilized. This process may become interrupted when thyroid dysfunction occurs, depending on the condition. [5]

There are two types of thyroid gland dysfunction:

  • Hyperthyroidism – Hyperthyroidism is when the thyroid becomes overactive. Essentially, the overactive thyroid will flood the body with too many hormones, which include triiodothyronine (T3) and thyroxine (T4). This condition will typically cause hypomenorrhea, a term for abnormally low menstrual bleeding or a lack of it entirely. As a result, ovulation may also become irregular, particularly if the endometrial lining fails to develop properly, impacting fertility. [6] In addition to irregular bleeding, women and people AFAB may also experience other overactive thyroid symptoms such as weight loss, muscle weakness, nervousness or irritability, heat intolerance, frequent bowel movements, and/or a rapid or irregular heartbeat. [7]
  • Hypothyroidism – Hypothyroidism refers to an underactive thyroid, meaning the thyroid gland doesn’t produce enough hormones. People with hypothyroidism can experience a condition called ‘oligomenorrhea’ (infrequent blood flow) or ‘menorrhagia’ (heavy blood flow that lasts longer than seven days). [1] Low levels of thyroid hormones can prevent the release of an egg, as well. [5] Due to the hormone imbalance, menstrual irregularity can be a symptom of an underactive thyroid. Hypothyroidism may manifest as fatigue, weight gain, cold intolerance, joint and muscle pain, slowed heart rate, and/or depression. [8]

So, what can you do if you’re experiencing thyroid issues and menstrual cycle irregularities?

Speak to a healthcare provider. They can order a blood test to measure your thyroid hormone levels and can help you to take the appropriate actions in terms of treatment and medication.

Thyroid Medications and Their Impact On the Menstrual Cycle

Your treatment plan will depend on your thyroid condition or dysfunction. For those with hyperthyroidism, anti-thyroid medications are typically prescribed. These may include [9]:

  • Propylthiouracil (PTU)
  • Methimazole (Tapazole)

These medications work to decelerate the production of thyroid hormones and can take effect within weeks. Accordingly, they can help reregulate the menstrual cycle to stimulate normal blood flow and regular ovulation. That said, stopping treatment can lead to a resurgence of symptoms. More permanent treatment options can include iodine treatment or surgical removal of the thyroid; however, these options can also lead to an underactive thyroid.

Beta-blockers may also prescribed, although they will only mitigate symptoms; they will not impact hormone production and therefore may not have an effect on the menstrual cycle. [9]

Those with hypothyroidism typically require the intervention of thyroid hormone replacement, which is available in four forms [9]:

  • Levothyroxine (Synthroid, Levothroid, Levoxyl, Unithroid)
  • Liothyronine (Cytomel)
  • Liotrix (Thyrolar)
  • Natural thyroid (Armour Thyroid, Nature-throid, Westhroid)

Similar to anti-thyroid medications, thyroid hormone replacements help balance thyroid hormone levels. They do this by supplementing the body with thyroid hormones. That said, an incorrect dosage can lead to hyperthyroidism, and regular monitoring of hormone levels by a healthcare provider is recommended. [9]

Understanding the Impact of Thyroid Medication

While a thyroid condition can lead to an irregular menstrual cycle, medication can help restore a cycle and balance hormones. When taken responsibly and at the correct dosage, thyroid medications will rarely, if ever, negatively impact your menstrual cycle.

That said, in the case of thyroid hormone replacements, it’s important to ensure that you’re not getting too much thyroid medication, which can tip the scales in the opposite direction. Similarly, thyroid removal or iodine treatment for hyperthyroidism can lead to decreased thyroid hormone levels, which can impact the menstrual cycle unfavorably. [9]

If you’re currently on thyroid medication or experiencing symptoms related to thyroid dysfunction, Everlywell provides an at-home Thyroid Test that can measure your current levels of thyroid hormones and thyroid antibodies.

With just a finger prick and a postage stamp, you can receive healthcare provider-reviewed test results and a digital consultation, if your results come back irregular. If you’re looking for more guidance, our online thyroid services can pair you with a licensed healthcare provider to meet with you to hear your concerns. These licensed healthcare providers can also provide you with prescriptions and additional resources so that you can better understand your condition.

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  1. Jacobson MH, Howards PP, Darrow LA, et al. Thyroid hormones and menstrual cycle function in a longitudinal cohort of premenopausal women. Paediatric and Perinatal Epidemiology. 2018;32(3):225-234. URL. Accessed June 12, 2023.
  2. Cleveland Clinic. Thyroid Disease: Hypothyroidism & Hyperthyroidism | Cleveland Clinic. Cleveland Clinic. Published April 19, 2020. URL. Accessed June 12, 2023.
  3. Adlersberg MA, Burrow GN. Focus on Primary Care Thyroid Function and Dysfunction in Women. Obstetrical & Gynecological Survey. 2002;57(Supplement):S1-S7. URL. Accessed June 12, 2023.
  4. Cleveland Clinic. Thyroid: What It Is, Function & Problems. Cleveland Clinic. Published June 7, 2022. URL. Accessed June 12, 2023.
  5. Orsu P, Koyyada A. Role of hypothyroidism and associated pathways in pregnancy and infertility: Clinical insights. Tzu Chi Medical Journal. 2020;32(4):312. URL. Accessed June 12, 2023.
  6. De Sanctis V, Soliman AT, Tzoulis P, et al. Hypomenorrhea in Adolescents and Youths: Normal Variant or Menstrual Disorder? Revision of Literature and Personal Experience. Acta bio-medica : Atenei Parmensis. 2022;93(1):e2022157. URL. Accessed June 12, 2023.
  7. National Institute of Diabetes and Digestive and Kidney Diseases. Hyperthyroidism (Overactive Thyroid) | NIDDK. National Institute of Diabetes and Digestive and Kidney Diseases. Published 2019. URL. Accessed June 12, 2023.
  8. Hypothyroidism (Underactive Thyroid) | NIDDK. National Institute of Diabetes and Digestive and Kidney Diseases. Published March 2021. URL. Accessed June 12, 2023.
  9. Thyroid Medications. Johns Hopkins Lupus Center. URL. Accessed June 12, 2023.
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