Hyperthyroidism, commonly called ‘overactive thyroid,’ occurs when too many thyroid hormones are produced by the thyroid, a butterfly-shaped gland at the base of the front of your neck .
The condition can develop at any age and in both females and males. However, women are diagnosed more often than men.
Here’s what you need to know about hyperthyroidism in females.
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The overall prevalence of hyperthyroidism in the US population is roughly 1.3%.¹ However, hyperthyroidism and hypothyroidism are more common in females than males.
Prevalence spiked to 4%–5%² in older females in one study, while another report found that women are 5–10 times³ more likely to be affected by the condition than males.
Although hyperthyroidism can be diagnosed in both females and males, the symptoms can vary by gender.
The general symptoms of hyperthyroidism can include:
Feeling tired and weak
Unexpected weight loss even with an increase in appetite
Heat intolerance and sweating
Irregular heartbeat and palpitations (fast-beating)
Trembling or twitching
Frequent bowel movements
An enlarged thyroid gland (goiter)
However, a common symptom specific to women is menstrual cycle changes.
Menstrual cycle changes
Women with thyroid disorders often experience menstrual cycle changes such as:
Light menstrual flow
Severe pain and cramps
Irregular menstrual timing.
In a study of 586 patients with hyperthyroidism, menstrual disturbances were found in 23.5% of severe hyperthyroidism cases and 16.3% of mild or moderate cases.
The prevalence of low menstrual flow was 3.7% in the severe group, much higher than in the healthy group (0%).
In another study⁵ of 50 women with a menstrual disturbance between the ages of 15 and 45, researchers found that 44% had a thyroid disorder.
Although both males and females can experience thyroid/thyrotoxic crisis, also known as a ‘thyroid storm,’ it is more common among women. This is because it is mostly associated with underlying Graves’ disease, which is more prevalent among women than men.
A thyroid storm is a dangerous situation in which your body produces an excessive amount of thyroid hormones (THs) that can lead to problems with the function of your organs.
Some common symptoms to look out for include:
Rapid heart rate
Loss of consciousness
The condition is rare, but if it happens, it can be fatal in 10%–20% of cases. Immediate medical care is required.
Another potential complication of hyperthyroidism among females is infertility. According to a recent study⁶ on the impact of thyroid disease on fertility, thyroid hormones play an essential role in ovarian function.
Thyroid hormones may also indirectly influence fertility. Even the mildest failure in thyroid function can affect potential fertility and pregnancy outcome complications.
Uncontrolled hyperthyroidism has been associated with an increased risk of:⁷
Low birth weight
Early pregnancy loss
These potential complications do not occur in all cases of hyperthyroidism. However, if you have been diagnosed and suspect it may be causing fertility issues, make an appointment to discuss it with your doctor.
Most of the following causes cannot be prevented. However, knowing the causes behind the condition can ensure you have a more informed conversation with your doctor, leading to early detection and treatment.
Causes of hyperthyroidism include:
Graves’ disease is an autoimmune disease that results in your immune system attacking your thyroid gland, causing it to produce too much thyroid hormone.
It is the most common cause of hyperthyroidism, affecting approximately one in 200 people.
The National Institute of Diabetes and Digestive and Kidney Disease (NIDDK) adds that around four out of five cases of overactive thyroid in the US result from Graves’ disease, with women older than 30 accounting for most of the cases.
Thyroiditis is inflammation and damage to thyroid cells that could happen as a result of several conditions such as:
Thyroiditis as a result of taking certain medications
If the damage to your thyroid cells is a slow process, you can develop hypothyroidism. If the process is rapid, the thyroid hormones stored in the cells will leak and can make their way into your blood at higher levels, leading to hyperthyroidism.
There are no symptoms unique to thyroiditis, but depending on whether your thyroid hormone production increases or decreases — you can expect to experience symptoms associated with hyperthyroidism or hypothyroidism.
Most thyroid nodules aren’t serious, don’t present any symptoms, and don’t require treatment. They are mainly discovered accidentally, but some people might notice a lump at the front of the bottom of their neck.
These lumps are often benign, but they can contain cancerous cells. Typically, whether the lump is benign or cancerous, the thyroid hormones are not usually impacted, but sometimes the nodule may produce an excess of thyroid hormones, leading to hyperthyroidism.
When this happens, your doctor will likely treat the problem with surgery or medication.
Medications/diets with excessive iodine
Excess iodine is another common cause of hyperthyroidism among women, as it can lead to over- or under-production of thyroid hormones. Under-production of the hormone leads to hypothyroidism, while increased production leads to hyperthyroidism.
According to one study,⁸ although iodine-induced hyperthyroidism can happen to anyone, people with pre-existing thyroid disease or who were previously exposed to iodine deficiency may be more susceptible.
Iodine-induced hyperthyroidism for some people can be very dangerous, sometimes even life-threatening, especially if not diagnosed or treated.
You can intake excess levels of iodine through certain medications and foods, including:
As we’ve seen, being female is a risk factor in itself, but other factors can put you at increased risk from hyperthyroidism.
Your family history is a potential risk factor for hyperthyroidism.
Although more research is needed to understand the genetic variations that contribute to diagnosis, the genetic element of thyroid disorders has been documented in many studies.
For example, a large-scale study⁹ using the national registry in Sweden has looked at the familial incidence of Graves’ disease. It reported that, among 29,005 offspring diagnosed with Graves’ disease, 1,771 (6.1%) first-degree relatives (parents or siblings) had the same diagnosis.
Those who had Graves’ disease were more susceptible to one or more 24 other autoimmune disorders.
Women who are smokers have a higher risk of being diagnosed with hyperthyroidism than non-smokers and those who have quit.
Studies¹⁰ have confirmed that smoking significantly impacts Graves' disease and hyperthyroidism.
Smoking increases the risk of developing the disease and having a goiter, and possibly reduces the effectiveness of treatment. One study¹¹ even reported that women who were smokers had almost twice the prevalence of hyperthyroidism compared to non-smokers.
Although it isn't very common, the hormonal changes in pregnancy can contribute to a hyperthyroid diagnosis.
One study¹² suggests this could be due to:
Increased excretions of iodine in urine (may increase thyroid volume in response)
An increase in thyroxine-binding globulin in the first trimester
Changes in the immune system
The first step to being diagnosed with hyperthyroidism is identifying symptoms and discussing them with your doctor.
Since it is common for older women not to display any signs of the condition, it is recommended to discuss any potential risk factors or concerns with your doctor.
If you are concerned that you or someone you know may have hyperthyroidism, you can expect to undergo blood tests to check your thyroid hormone levels. These hormones are:
Your healthcare provider will compare your results with the normal levels of women of similar age and condition. They may also examine blood tests for antithyroid antibodies (common among people with Graves' disease).
Your diagnosis will be based on clinical findings and confirmed by one or more of the following:
Biochemical tests: Screening tests for TSH, T4, T3, thyroid autoantibodies, thyroglobulin, and calcitonin
Imaging techniques: Radioactive iodine uptake scans and/or ultrasounds to identify any potential lumps on your thyroid and to examine the size/shape of your thyroid
Hyperthyroidism treatment will depend on factors including:
The cause of the condition
Other existing conditions you may have (including pregnancy)
Your ability to take certain antithyroid drugs (i.e., allergies)
The goal is to decrease your thyroid-hormone production to a more desirable level. Your doctor will likely discuss these three options with you:
These will be beta-blockers or antithyroid drugs. Beta-blockers can be good for reducing some symptoms within hours and making you feel better but will not stop the overproduction of thyroid hormone.
Antithyroid drugs, however, are used to reduce the production of thyroid hormones and can clear the symptoms permanently in some cases, while in others, they can only relieve symptoms temporarily.
These medications often have side effects to consider and can take up to months to work.
Radioiodine therapy is another effective treatment option for hyperthyroidism. It comes in the form of a drink or capsule and will kill or reduce the size of your thyroid cells.
This treatment permanently destroys a large portion of the thyroid gland, which can cause the majority of patients to have hypothyroidism eventually. They will often continue with thyroid hormone replacement treatments for the rest of their lives.
This is not a possible treatment for pregnant women.
Another option is thyroid surgery, which removes parts of your thyroid gland. This method is often used for people with big goiters or who are pregnant and cannot take the preferred medication.
The downside is that, like radioiodine therapy, it will result in hypothyroidism and lifetime treatment with thyroid hormones.
You should discuss all the pros and cons of each treatment with your doctor when determining which option is the best for you.
Hyperthyroidism in pregnancy is most commonly due to Graves’ disease, with about 2.5 to 5.9 in 1,000 pregnant women in the US ¹³ having the condition each year.
A large-scale study in Denmark ¹⁴ identified that, during pregnancy, the first trimester has the highest risk and the third trimester has the lowest. In contrast, in postpartum stages, the highest risk of hyperthyroidism was around seven to nine months after delivery.
Treatment is not essential in all cases and varies from person to person depending on:
Your medical history
The severity of your condition
What stage of pregnancy you're at
You must discuss all your options with your doctor to ensure you receive the best treatment for your needs.
Management and monitoring are crucial during pregnancy since there is an increased risk¹⁵ of:
Low birth weight
For this reason, treatment for hyperthyroidism during pregnancy is often different from treatment in women who are not pregnant.
The most common antithyroid drugs prescribed during pregnancy are:
Methimazole or carbimazole
It is important to note that all antithyroid medications have been linked, in some cases, to congenital disabilities,¹⁶ particularly when taken in the first trimester, with methimazole having the highest rate.
Drug treatment is then followed up with regular monitoring every four to six weeks (even postpartum) to determine the appropriate dosage. The baby is checked for thyroid dysfunction following birth.
If you have been diagnosed with a hyperthyroid condition, you should see your doctor regularly to monitor your condition and make treatment adjustments as needed.
If you have not been diagnosed with hyperthyroidism and suspect that you may have it, discuss all your symptoms with your doctor since many can be similar to other conditions.
If you experience unexpected weight loss and/or swelling at the base of your neck, you should see your doctor as soon as possible. They will be able to help identify if hyperthyroidism is the cause. If not, they will work with you to find out what is causing it and how to treat it.
If you experience any symptoms that could indicate a thyroid crisis, call 911 immediately.
Although both men and women can be diagnosed with hyperthyroidism, the condition is more common among females.
It is crucial that women with risk factors — such as a family history of any thyroid disorder, pregnancy or postpartum, and smoking — discuss any potential symptoms with their doctor.
For women specifically, in addition to the general symptoms, menstrual irregularities and inability to conceive or early pregnancy loss could be caused by the condition.
Fortunately, management and treatment options can improve your quality of life and even offer a cure for some patients.
Radioiodine therapy has the highest success rates, although some people may consider thyroid surgery. Antithyroid drugs are also an option.
Since everyone is different and requires different solutions, consult your doctor first for the best treatment for you and your condition.
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