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Get to know your thyroid: where it is, what it does, and why it

Get to know your thyroid: where it is, what it does, and why it's important

8 min read

Though the thyroid is a little butterfly-shaped gland that lives at the front of the neck (right under your voice box), it does a whole lot more than its size and location may suggest. In fact, this tiny gland is a powerful player in our overall health — including our fertility.

Below, we’ll cover the basics and explain why it’s so important to know about this small-but-mighty gland.

Here’s what you’ll learn

  • Why the thyroid gland is a hugely important part of your body running like a well-oiled machine
  • What can happen when your thyroid gland isn’t operating as usual
  • Why people get thyroid disorders
  • How thyroid disorders are typically treated
  • How you can stay on top of thyroid function on your own or with a doctor

Thyroid gland 101

The thyroid gland is part of the endocrine system — a motley crew of glands that runs the body’s hormone production. This gland covers a lot of ground. For one, it helps regulate function by releasing hormones into the bloodstream when you need them most: When you need more energy, like while pregnant or when you feel cold, the thyroid pumps out more hormones to help. Basically, the thyroid has your back.

The thyroid regulates and affects almost every part of the body, including the following:

To keep these systems in check, the thyroid releases three super important hormones:

  • Triiodothyronine (or T3), and thyroxine (or T4): Both of these hormones are made in the thyroid’s follicular epithelial cells (found at the surface of the organ), which are basically the powerhouse of the gland. They’re impacted by how much iodine we get in our food. (These days, iodine is often added to table salt.) Their role? Increasing the basal metabolic rate, aka how fast and hard our cells work for us. T4 can be found in the body in two forms: bound T4 and free T4 (FT4 — one of the hormones Modern Fertility can test for).
  • Calcitonin: Produced by the other type of cells in the thyroid, parafollicular cells (which live inside the organ), this hormone is involved in calcium and bone metabolism.

There’s no question that the thyroid gland is a hard worker — but the pituitary, a pea-sized gland known as the “master gland,” is pushing some of the levers of thyroid hormone production. Because we sometimes need more or less hormones produced, the pituitary gland sends a helpful message (via thyroid-stimulating hormones, or TSH) to release the right amount into the bloodstream. (Good looking out, pituitary.)

Thyroid disorders (or when your thyroid is dysregulated)

According to Dr. Cindy Duke, reproductive endocrinologist and medical director of the Nevada Fertility Institute, the thyroid is responsible for our bodies’ “get up and go.” As she explains it, “For a lot of people who are diagnosed with thyroid disease, it’s either they have too much get up and go, or they have too little get up and go.

What that means hormonally speaking: When the thyroid is overactive and produces too much T4, the pituitary gland sends a message (with low levels of TSH) to make less. When the thyroid is underactive and produces too little T4, the pituitary gland sends a message (with higher levels of TSH) to make more. It’s estimated that 20 million Americans have thyroid disorders — but up to 60% are unaware of their condition. It’s also worth noting that women are way more likely than men to have dysregulated thyroids — and the risks increase after childbirth. (One in eight will develop problems at some point in their lives, according to the American Thyroid Association.)

Here’s an interesting fact about the prevalence of thyroid disorders: According Dr. Duke, “You tend to see more thyroid disorders in areas with higher levels of baseline nuclear radiation.” In her home state of Nevada, nuclear testing from World War II contributed to more subclinical (fewer symptoms and less easily diagnosed) thyroid disorders among residents. This is because nuclear radiation exposure sends radioactive iodine into the bloodstream — the body can’t distinguish between the iodine created by the body and iodine from other sources — and kills thyroid cells. (When someone is diagnosed with thyroid cancer, radioactive iodine is often used in treatment.)

The impact of thyroid disorders

If women experience thyroid conditions, there are a few unique ways they can be impacted:

  • Out-of-control menstrual cycle: The thyroid helps kick our menstrual cycles into gear, so too high or too low thyroid hormone levels can lead to very light, heavy, or irregular periods. Imbalance can also cause amenorrhea (when your period stops for months or longer).
  • Fertility issues: Thyroid disease can change your menstrual cycles, so it also has an effect on ovulation. If ovulation is disrupted or stopped, it’s harder to get pregnant. If you also have an autoimmune disorder leading to a thyroid disorder like Hashimoto’s disease or Graves’ disease, your fertility may be impacted as well. Some autoimmune diseases are polyglandular, meaning they affect multiple glands that produce hormones, including ovaries.
  • Problems during pregnancy: There can be difficulties for both the mother and the baby, including premature birth, preeclampsia, thyroid storm (sudden worsening of related symptoms), increased heart rate in the newborn, low birth weight, miscarriage, anemia, stillbirth, or problems with the baby’s development.

But thyroid problems don’t just impact your reproductive system. If they go unaddressed, that could lead to the following health problems:

  • Cardiovascular issues: When you have too little thyroid hormone, your heart rate can slow down and your blood pressure can rise. On the other hand, if you have too much thyroid hormone, your heart rate can increase and lead to arrhythmia (an abnormal heartbeat), or result in high blood pressure.
  • Osteoporosis: The thyroid plays a role in the rate of bone loss, so when there’s too much T4, that loss speeds up — and osteoblasts (the cells responsible for bone formation) can’t replenish the bones at the same pace.

When you have an overactive or underactive thyroid

Your thyroid can be deregulated in one of two ways: an increased or decreased production of hormones, which both often lead to diagnosable (and easily treatable) conditions. In either of these cases, there’s the possibility that thyroid activity can be within the range of “normal,” and therefore more difficult to diagnose, but still cause problems. In this section, we’ll break it all down for you.

Low TSH levels and hyperthyroidism

When the thyroid gland produces too many hormones, or is overactive, it’s known as hyperthyroidism. If you have hyperthyroidism, you could experience a wide range of symptoms (some of which overlap with other conditions and can make diagnosis all the more difficult). Here are the symptoms of hyperthyroidism:

  • Unintentional or unexpected weight loss
  • Rapid heartbeat, or tachycardia
  • Irregular heartbeat, or arrhythmia
  • Pounding of the heart, or palpitations
  • Increased appetite
  • Anxiety and irritability
  • A slight tremor in the hands or fingers
  • Sweating
  • Changes in the menstrual cycle
  • Changes in bowel movements
  • An enlarged thyroid (or goiter)
  • Skin thinning and brittle hair

To get diagnosed with hyperthyroidism, a doctor needs to go over your medical history and conduct a physical exam (including a throat check for swelling or enlargement of the thyroid gland). A blood test will also be taken to confirm reduced levels of TSH, and sometimes to also look at T4 levels. Doctors also test for TRAb antibodies in order to diagnose overactive thyroid. (Heads up: If you’re taking biotin, which is found in many supplements, a blood test may show falsely high levels.)

You can also have what experts call subclinical hyperthyroidism, where the symptoms are less noticeable. In subclinical hyperthyroidism, the T3 and T4 levels are elevated, but the TSH level is just south of normal. (According to Dr. Duke, subclinical hyperthyroidism and hypothyroidism have only really been talked about in the medical community for the past ten years — though both diagnoses make up the majority of thyroid dysfunction cases.)

High TSH levels and hypothyroidism

On the flip side, when the thyroid produces too few hormones, or is underactive, it’s called hypothyroidism. Here are the symptoms of hypothyroidism:

  • Fatigue
  • Increased sensitivity to cold
  • Constipation
  • Dry skin
  • Weight gain
  • A puffy face
  • Voice hoarseness
  • Muscle weakness, aches, and stiffness
  • Elevated blood cholesterol level
  • Joints pain or swelling
  • Heavier or irregular menstrual periods
  • Coarse hair and hair loss
  • Brittle nails
  • Slowed heart rate
  • Depression
  • Impaired memory
  • Enlarged thyroid gland (goiter)

The diagnosis for hypothyroidism is the same as hyperthyroidism: through blood tests that measure TSH (and sometimes T4) and a look into any reported symptoms.

Hypothyroidism can also be subclinical, or have less noticeable symptoms — in these cases, the T4 level normal, but the TSH level is elevated.

Why people get thyroid disorders

There are a few things that can cause the thyroid to become dysregulated:

  • Graves’ disease: In this autoimmune disease, the immune system attacks the thyroid gland and makes it go into overdrive with hormone production, which can often result in an enlargement of the thyroid gland and hyperthyroidism. (This is the most common cause of hyperthyroidism.)
  • Hashimoto’s disease: This hereditary condition, which affects the immune system, can cause Hashimoto’s thyroiditis (more on thyroiditis below!), which in turn can cause hypothyroidism. When someone has Hashimoto's, the body produced antibodies that attack the thyroid gland and impair its ability to produce hormones (in fact, doctors will often test for TPO antibodies to confirm a Hashimoto's diagnosis). Hashimoto's is the most common cause of hypothyroidism.  
  • Overactive nodules: There may be nodules within the thyroid gland that become overactive and lead to excess hormone production. One single nodule that does this is called toxic autonomously functioning thyroid nodule, while several can join together to form a toxic multinodular goiter. Thyroid nodules are super common (present in up to 50% of people), but there’s only a 6-8% chance that one will lead to thyroid cancer. That said, nodules can be found in 25% of people with Graves’ disease.
  • Thyroiditis: This disorder is an inflammation of the thyroid gland that can be painful or painless, the latter of which often occurs after childbirth (postpartum thyroiditis). It can also reduce the number of hormones produced.
  • Iodine intake: When the body gets too much iodine, the thyroid can start to produce too many hormones. Though an iodine deficiency can cause hypothyroidism, the introduction of iodized salt in the ‘50s minimized the risk. (Here’s looking at you, girl under the umbrella on the Morton’s salt container!)
  • Non-functioning thyroid gland at birth: 1 in 4,000 newborns is born with thyroid dysfunction, but screening blood tests in the hospital can evaluate this early on.

Treating thyroid disorders

Thyroid disorders are treatable, but they often require more lab testing (potentially repeating the hormone test and doing the antibody test).

The treatments for hyperthyroidism depend on your age, physical condition, the underlying cause, your personal preference, and the severity, but include: radioactive iodine, antithyroid medications, beta blockers, and surgery (a thyroidectomy, or removal of the thyroid gland).

If you experience hypothyroidism, the standard treatment is daily usage of a synthetic thyroid hormone, like levothyroxine (Synthroid is a common one).

Dr. Duke says that the main lifestyle change that could improve thyroid function is how much iodine you’re getting in the foods you eat. “If someone is inadvertently eating iodine-poor foods, meaning not a lot of iodine, that may be one thing you can change that could ‘naturally fix’ your thyroid if you’re experiencing symptoms of subclinical hypothyroidism,” she explains. If you’re taking in too much iodine through what you eat or treatment for thyroid dysfunction, and your body isn’t used to that much iodine, that could also either cause or worsen symptoms. (Here’s a full list of iodine-rich foods.)

How can you stay on top of your thyroid?

Dr. Duke suggests checking in with how you’re feeling to stay on top of any thyroid-related symptoms. (And while most people won’t be able to feel the size of their thyroid gland, if there’s swelling in the neck, that could be a sign of a goiter or nodules.)

If you find that you’re experiencing any of the symptoms we listed for hyperthyroidism or hypothyroidism, Dr. Duke recommends scheduling a visit with your healthcare provider — especially if you have:

  • Had thyroid issues in the past
  • Had surgery or radiotherapy that could affect the thyroid gland
  • Had a condition like a goiter, anemia, or type 1 diabetes (which is an autoimmune disease)

The Modern Fertility test is also a great way to touch base with your thyroid and its function. Depending on what birth control you take, your test could measure TSH and fT4 levels, two of the hormones produced by the thyroid. That way, you can take a look at your thyroid without heading into the doctor’s office (or changing out of your PJs).

For more info, watch our Q&A with Dr. Cindy Duke below.

This article was medically reviewed by Dr. Eva Marie Luo, an OB/GYN at Beth Israel Deaconess Medical Center and a Health Policy and Management Fellow at Harvard Medical Faculty Physicians, the physicians organization affiliated with the Beth Israel-Lahey Health System.

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Sarah duRivage-Jacobs

Sarah duRivage-Jacobs is a writer and editor at Modern Fertility. She lives with her creamsicle cat, Jasper, in New York City and doesn't believe in the concept of TMI.

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