The thyroid gland is a small butterfly-shaped organ residing in front of the throat. In healthy individuals, it releases thyroxine (T4) and triiodothyronine (T3), which comprise thyroid hormone, into the blood. Such hormones facilitate many functions within the body, including metabolism, temperature regulation, energy levels, and skin, hair, and nail growth.
However, some individuals may develop thyroid gland issues that can negatively impact these functions, in addition to many others. Thyroid dysfunction usually occurs with either overproduction or underproduction of thyroid hormone. Thyroid disease can happen in any individual; however, it is more prominent in some populations, especially females.
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Thyroid diseases can seriously affect both women's and men's health. However, estimates put women at around 5 to 8 times greater likelihood of experiencing a thyroid-related issue than men.¹
While women are generally more likely to develop both hypothyroidism and hyperthyroidism than men, some women experience an even higher risk of developing thyroid disease.
In particular, women of smaller stature and lower body mass index in childhood and adolescence are far more likely to develop hypothyroidism than other women. Women over the age of 60, those who are pregnant, or women who have another autoimmune disorder, type 1 diabetes, or a family history of thyroid issues are also more likely to develop thyroid diseases.
It is important to regularly get your thyroid hormone levels checked if you fall into any of these categories, as they place you at a higher risk of thyroid complications.
Any and all thyroid-related diseases can affect women. While the symptom presentation may vary between the sexes, the diseases themselves tend to be similar. They include:
Women are more likely than men to develop thyroiditis, thyroid nodules, thyroid cancer, and disorders causing hypothyroidism and hyperthyroidism.
One disease that is specific to women is postpartum thyroiditis. Those who have given birth are at risk of developing this condition, which affects around 10% of women post-birth and causes thyroid inflammation, fatigue, and moodiness, often mistaken for postpartum depression.
Many thyroid-related issues are similar between men and women, with an excess of thyroid hormone tending to speed many of the body's processes. This can cause nervousness, anxiety, hyperactivity, unexpected weight loss, and sensitivity to heat.
A lack of thyroid hormone, however, can cause a general slowing of metabolism, fatigue, sensitivity to cold, weight gain, and dry skin.
There are many issues caused by thyroid disease that are specific to females. These include issues with the menstrual period, resulting in a light, irregular, or very heavy periods. An imbalance in thyroid hormones can also cause periods to stop. Thyroid disease can also result in problems becoming pregnant and during pregnancy.
Thyroid diseases can interfere with a woman’s ability to ovulate, create progesterone deficiency, or disrupt pituitary hormones, all of which can alter the menstruation process.
Hypothyroidism, in particular, can mean that the ovarian follicles develop poorly, estrogen cannot be cleared properly, and insulin sensitivity is impaired, which can cause polycystic ovarian syndrome (PCOS).
Even in individuals with healthy thyroids, the circulating thyroid hormone can affect sex hormone levels. This can be associated with differences in menstrual cycle function.
Excess or lack of thyroid hormone can alter the levels of sex hormone binding globulin (SHBG), gonadotropin-releasing hormone, and sex steroid levels. This has an adverse effect on menstruation and fertility.
Menstruation itself may also have an effect on circulating thyroid hormone levels. Major releases of thyroid-stimulating hormone (TSH) occur in response to high estradiol levels in the middle of a woman’s menstrual cycle.
Both hyper- and hypothyroidism can cause anovulation, or lack of ovulation, in females. This means an egg (ovum) is not released from the ovaries within the menstrual cycle. As an egg is required for pregnancy to occur, this means that if anovulation is chronic, then the female is infertile (cannot get pregnant).
In some cases, this causes excessive shedding of the uterine wall and heavy bleeding. In cases of uncontrolled hypothyroidism, disordered growth of this uterine lining can occur, which also leads to heavier-than-usual periods.
Those with thyroid issues also have changes to their coagulation factors, which means their body isn’t able to adequately clot blood. This can cause many issues with bleeding, including heavier menstrual periods.
Research has illustrated this by demonstrating that thyroid problems in adolescents prompt heavier-than-usual menstruation. Such an issue can cause significant detriment to the quality of life and can be highly troubling, limiting the activities able to be performed when menstruating.²
Patients experiencing hypothyroidism can also experience hyperprolactinemia, or excess of prolactin hormone. This can cause a thinning of the uterine wall, which means the egg finds it more difficult to implant.³
This can present as extremely light periods. Changes in prolactin hormone levels can also cause menstrual periods to stop altogether or occur infrequently.
As mentioned, both hyper- and hypothyroidism can cause anovulation. This means that pregnancy cannot occur, as no egg is released to be fertilized. Changes in sex hormone levels may also alter the sex drive of these individuals, meaning they are less likely to become pregnant.
However, it is important to note that while many individuals may worry that changes in menstruation mean reductions in fertility, this is not always the case.
Hypothyroidism is a condition in which the thyroid gland is underactive, meaning less thyroid hormone is secreted into the blood. This can cause various widespread issues, including changes in development, metabolism, and ability to regulate heat.
Irregular periods occur when the length of each menstrual period varies. Such irregularities are not always caused for concern. In most cases, when women begin getting their period or when they enter menopause, they experience a variance in length between menstruation cycles.
Certain medications, namely hormonal birth control, can also alter the length between periods. Other causes of irregular periods that may be of concern include early pregnancy, excessive weight loss, or medical conditions such as polycystic ovary syndrome or thyroid disease.
While thyroid disorders aren’t the only cause of irregularities in periods, they are relatively common. Those experiencing worrying changes in their menstruation should consult their healthcare professional about possible thyroid conditions.
Hypothyroidism is likely to prompt some fertility and menstrual irregularities, namely heavy periods. This may be due to various factors, including issues with coagulation due to less thyroid hormone circulation or possibly irregular shedding of the uterine wall lining.
It is also common for women with hypothyroidism to experience amenorrhea or the absence of a menstrual period. As mentioned, this may be caused by changes in sex hormones due to the absence of thyroid hormones.
Studies have demonstrated that around 23% of women with hypothyroidism experience some form of menstrual irregularity, whether that be heavier periods, irregular period timing, or absence of period.⁴
While the symptoms of hypothyroidism vary from person to person, depending on the severity of the condition and different environmental factors, those with hypothyroidism might notice the following signs:
Sensitivity to cold temperatures
Muscle weakness and cramping
Dry skin, hair, and nails
Tingling or numbness of the extremities
Loss of sex drive
If you are experiencing any of the above symptoms, it may be time to get your thyroid hormone levels checked.
Having hypothyroidism may reduce your fertility. For a woman to become pregnant, she must be inseminated during her ovulatory phase, and the egg must be able to implant in the uterine wall.
When an individual has hypothyroidism, she may experience a shorter luteal phase, which is the length between ovulation and shedding of the uterine wall (menstrual period). This means that even if the egg is fertilized, the embryo may not be able to implant in time, and the woman may not become pregnant.
Hypothyroidism, if left untreated, may also increase the risk of miscarriage. Thus, it is highly important to have your thyroid examined if you plan to become pregnant or are experiencing irregular periods.
Getting regular checkups of your thyroid is important, especially if you are experiencing any irregularities in your period. The early stages of hypothyroidism are named subclinical hypothyroidism. This condition consists of slightly altered TSH levels that do not yet meet the requirements for hypothyroidism diagnosis.
While this condition usually doesn’t cause irregularity in periods, it can cause issues with pregnancy and some irregular bleeding or spotting. If left untreated, it can develop into overt hypothyroidism, which will likely cause issues with fertility, menstruation, and the pregnancy process.
Hypothyroidism is diagnosed by a healthcare professional, often with a thyroid function test. This test involves taking a blood sample and examining the levels of thyroid stimulating hormone (TSH) and T4 present.
Low levels of T4 and contrastingly high levels of TSH may indicate the presence of hypothyroidism. Regular blood tests are often recommended to monitor any possible changes to these hormone levels.
A less common way that hypothyroidism can be diagnosed is through a thyroid antibody test. This checks for the presence of antibodies to thyroid hormones and is used if an autoimmune condition is suspected.
Once hypothyroidism has been diagnosed, it can be treated with medication, the most common of which is levothyroxine. Luckily, this medication is effective and easy to take in most circumstances, only requiring a single pill taken once a day.⁵
This medication is a synthetic version of the thyroid hormone and functions to replace the levels your body is not naturally and adequately producing. The restoration of thyroid hormone levels through levothyroxine can help to mitigate many of the symptoms of hypothyroidism.
Your healthcare professional will ensure the correct dosage for you is achieved. It is important to note that getting the dose right may take time and frequent blood testing to ensure thyroid levels are back to their normal state.
If the cause of your menstrual irregularities is due to imbalances in your thyroid hormone levels, then treatment of this condition through hormone replacement is likely to improve these symptoms.
If thyroid hormones can be restored to their normal levels, the balance between reproductive function and thyroid hormones will also return to normal, facilitating regular periods.
However, if your menstruation issues have a different origin than thyroid disease, the treatment of this condition is not likely to improve your periods. Issues such as low BMI or PCOS will require alternative treatments.
While irregularities in menstruation can be caused by a variety of health issues, it is important to consider the relationship between your thyroid and menstruation. If you experience irregular periods, hypothyroidism may be the cause.
This condition can cause issues with fertility and possibly increase the risk of miscarriage. It is extremely important to get your thyroid checked if you experience any changes to your menstruation.
General information/press room | American Thyroid Association
Levothyroxine | NHS
Thyroid disease (references) | Office on Women's Health
Hypothyroidism and pregnancy | Johns Hopkins Medicine
Thyroid antibodies test | Testing