Hyperthyroidism can lead to increased prolactin. This can interfere with the production of estrogen and progesterone, two hormones that help regulate your menstrual cycle.

Thyroid hormones help regulate your metabolism, energy levels, internal body temperature, hair growth, and more, says hormone specialist and integrative nutritionist Alisa Vitti, author of “In the FLO” and “WomanCode.”

When the butterfly-shaped gland at the base of your neck pumps too many of these hormones out, you can experience a wide variety of symptoms, including menstrual cycle irregularities.

“The thyroid helps control the menstrual cycle,” says Amy Myers, MD, author of “The Thyroid Connection” and “The Autoimmune Solution.”

”If you have too much thyroid hormone (hyperthyroidism) or not enough thyroid hormone (hypothyroidism), your periods will be disrupted,” explains Myers.

Hyperthyroidism, specifically, can cause your periods to be very light, irregular, and in some cases make you miss your period for several months at a time, she says.

“When your thyroid hormone levels increase, your brain starts to produce more prolactin,” says Vitti.

High levels of prolactin can interfere with the typical production of estrogen and progesterone, two hormones that help regulate your menstrual cycle.

“When prolactin levels are high, ovulation can be disrupted, which can lead to cycle irregularities,” explains Vitti.

High prolactin levels also suppress the production of gonadotropin-releasing hormone (GnRH).

When GnRH is released, it signals the pituitary gland to produce follicle-stimulating hormone (FSH) and luteinizing hormone (LH). If GnRH is suppressed, the pituitary gland halts the production of FSH and LH.

And FSH and LH influence the menstrual cycle. These hormones tell your ovary to release an egg. If these FSH and LH levels are low, an egg isn’t released.

The menstrual cycle is centered around the release of an egg from the ovary to the fallopian tube. So if this doesn’t happen, your overall cycle and menstrual period are disrupted.

Addressing the underlying condition usually resolves related menstrual symptoms.

“The first step in treating hyperthyroidism is figuring out if there are any underlying factors that are causing the thyroid to start producing too much thyroid hormone in the first place,” says Myers.

In some cases, overactive thyroid is caused by another underlying condition like Graves’ disease, thyroid nodules, or thyroid inflammation, she explains.

A healthcare professional may recommend a physical exam, thyroid ultrasound, blood test, and in some cases a radioactive iodine uptake test. This will help them discern if there is an underlying cause, as well as confirm that diagnosis.

If you have hyperthyroidism, you have a few options.

  • Radioactive iodine treatment: This involves drinking or ingesting a mixture of iodine and a low dose of radiation to destroy thyroid cells.
  • Medication: The condition can be managed with a few different types of medications, including thionamides.

Some clinicians recommend certain dietary changes, including a temporary elimination diet, an anti-inflammatory diet, or going gluten-free, says Myers.

“To support optimal thyroid function, some providers also recommend adding a multivitamin that contains thyroid-supporting minerals such as zinc, selenium, and iodine, along with vitamins C and E,” she adds.

“As soon as you feel that you have more than a few of symptoms associated with hyperthyroidism, you should go in for a thyroid panel with your general practitioner,” says Vitti.

You should also talk with a healthcare professional if you’re experiencing unexpected changes to your menstrual cycle.

The menstrual cycle was dubbed the ”fifth vital sign” by the American College of Obstetricians and Gynecologists in order to “reinforce its importance in assessing overall health status for patients and caretakers.”

In other words, if your menstrual cycle is off, there’s likely an underlying cause that needs to be evaluated — then treated — by a healthcare professional.

Why does the thyroid affect the menstrual cycle?

“Hyperthyroidism can cause elevated levels of prolactin,” says Vitti.

High prolactin levels can interfere with the production of estrogen and progesterone and suppress GnRH — both of which mess with your menstrual cycle.

Does hyperthyroidism make periods worse?

Any thyroid disorder can impact your period. However, it’s usually hypothyroidism that makes periods heavier — not hyperthyroidism.

More commonly, hyperthyroidism makes periods lighter. (Though, for the record, hypothyroidism can also make periods lighter).

Although lighter periods may sound nice, “it doesn’t actually feel good because it’s happening at the expense of other internal systems,” explains Kris Adair, family nurse practitioner and founder of Adair Family Clinic and MedSpa in Peoria, Arizona.

What are the other symptoms of hyperthyroidism?

Hyperthyroidism happens when thyroid hormones are too high.

“When your thyroid hormones are too high, it causes your metabolism to speed up, which leads your body to burn through nutrients too quickly,” notes Myers.

“This can result in malnutrition and lead to a wide range of problems,” she explains. ”A fast heart rate, sugar cravings, rapid weight loss, severe anxiety, hair loss, tremors, increased hunger, increased temperature, and hot flashes, to name just a few.”

What’s the difference between hyperthyroidism and hypothyroidism?

While hyperthyroidism is marked by the overproduction of thyroid hormones, hypothyroidism is marked by the underproduction of them. Both conditions can cause menstrual irregularities.

Hyperthyroidism can mess with your menstrual cycle, making your period lighter or even nonexistent. However, the condition can be treated.

So, if your menstrual cycle has been off — or you’re experiencing other symptoms of hyperthyroidism — talk with a healthcare professional.

A clinician will be able to administer the proper diagnostic tests to see if there is any underlying cause of your overactive thyroid, as well as help you come up with a treatment plan.

Gabrielle Kassel (she/her) is a queer sex educator and wellness journalist who is committed to helping people feel the best they can in their bodies. In addition to Healthline, her work has appeared in publications such as Shape, Cosmopolitan, Well+Good, Health, Self, Women’s Health, Greatist, and more! In her free time, Gabrielle can be found coaching CrossFit, reviewing pleasure products, hiking with her border collie, or recording episodes of the podcast she co-hosts called Bad In Bed. Follow her on Instagram @Gabriellekassel.