• Hypothyroidism

What Hormones are Produced in the Thyroid Gland?

Published: August 01, 2025
Updated: August 01, 2025
3 mins

The thyroid is a small, butterfly-shaped gland located at the base of your neck – but don’t let its size fool you. As a vital part of the endocrine system, the thyroid produces hormones that regulate many of your body’s most essential functions. From your metabolism and energy levels to your heart rate and even your bone health, the thyroid plays a central role in keeping everything running smoothly.

When the production of thyroid gland hormones becomes imbalanced, it can affect nearly every system in the body. Fatigue, weight changes, mood shifts, and weakened bones are just a few of the ways thyroid dysfunction can show up. That’s why understanding the purpose of thyroid hormones – and how they work – is such an important part of maintaining overall wellness.

In this article, we’ll break down the hormones produced by the thyroid gland, explain how they function, explore what happens when levels shift, and introduce thyroid hormone replacement therapy as a treatment for low thyroid hormone levels (hypothyroidism). This therapy will soon be available as part of our women’s health program, giving you convenient access to expert care and personalized support.

Hormones Produced in the Thyroid and Their Roles

There are three main hormones produced by the thyroid gland, each with a distinct role in your body’s internal balance:

1. Thyroxine (T4): T4 is the most abundant thyroid hormone in circulation. It acts as a storage hormone, containing four iodine atoms. On its own, T4 is relatively inactive – but it can be converted into the more active T3 in tissues like the liver and kidneys.

2. Triiodothyronine (T3):

T3 contains three iodine atoms and is the most active thyroid gland hormone. It helps regulate your metabolism, body temperature, heart function, and many other processes. Even though T3 is produced in smaller amounts than T4, it has a stronger effect on your body’s cells.

3. Calcitonin: Produced by specialized cells in the thyroid called C-cells, calcitonin helps regulate calcium levels in the blood. It reduces calcium levels by slowing the activity of cells that break down bone. While calcitonin has a more targeted role than T3 and T4, it plays an important part in maintaining strong bones and preventing excessive calcium loss.

Together, these hormones help keep your body’s systems in balance. When functioning properly, the thyroid gland hormones support everything from your mood to your bones – and understanding how they work is the first step toward supporting your long-term health.

The Purpose of Thyroid Hormones

The purpose of thyroid hormones extends far beyond just energy levels or metabolism. These powerful messengers travel through the bloodstream and influence nearly every cell, organ, and system in your body.

Regulate metabolism

One of the most well-known thyroid hormone functions is its role in controlling your metabolic rate. T3 and T4 determine how quickly your body converts food into energy, how fast your heart beats, and how much heat your body produces. If your thyroid hormones are too low, your metabolism slows down, often leading to fatigue, weight gain, and feeling cold. Too high, and your body can burn energy too quickly, causing weight loss, anxiety, and heart palpitations.

Support heart, brain, and digestive function

T3 and T4 help maintain the rhythm and strength of your heartbeat, support brain function and memory, and keep your digestive system moving. When thyroid hormone levels are imbalanced, these systems often feel the impact first – leading to symptoms like brain fog, constipation, or irregular heartbeat.

Influence mood and menstrual regularity

Thyroid hormones also affect emotional regulation and reproductive health. Low hormone levels can contribute to depression, irritability, and menstrual irregularities. Many women first learn about thyroid issues after noticing changes in their mood or cycle.

Promote bone health

While T3 and T4 manage metabolism and organ function, calcitonin plays a more specialized role in calcium balance. It lowers calcium levels in the blood by slowing the breakdown of bone tissue, helping to maintain healthy bones and prevent excess calcium loss. Though less discussed, calcitonin’s impact on bone regulation is particularly important as women age.

In short, thyroid hormones do much more than keep your energy up. They influence the way your entire body operates – from how you think and feel to how your organs function and how strong your bones remain. This is why maintaining thyroid hormone balance is essential for overall well-being.

How Thyroid Hormones are Made

The hypothalamus, a region in the brain, releases TRH (thyrotropin-releasing hormone), which signals the pituitary gland to produce TSH (thyroid-stimulating hormone). TSH then travels through the bloodstream to the thyroid and tells it to get to work.

Once stimulated by TSH, the thyroid gland uses iodine – a mineral found in food – to create T3 and T4. These hormones are made by follicular cells inside the thyroid. T4 is produced in greater quantities, but T3 is the more active form in the body. Much of the T4 made is later converted to T3 in the liver or kidneys. 

Calcitonin is made by parafollicular cells in the thyroid. While not as central to metabolism as T3 and T4, calcitonin plays a role in regulating calcium levels in the blood.

When Hormone Production Shifts

Thyroid levels don't always stay the same throughout life. Factors like aging, stress, pregnancy, and autoimmune conditions can all impact how much hormone the thyroid gland produces. When this balance shifts, it can affect everything from your energy levels to your metabolism, mood, and body temperature.   

Two of the most common thyroid disorders are:

• Hypothyroidism: This condition occurs when the thyroid does not produce enough hormones. This can lead to fatigue, weight gain, cold intolerance, dry skin, and slower thinking or movement. 

• Hyperthyroidism: This condition is caused by overproduction of the thyroid hormone. This often causes symptoms like weight loss, anxiety, rapid heartbeat, heat sensitivity, and trouble sleeping. 

A well-known cause for a decrease in thyroid hormone production is Hashimoto’s thyroiditis. Hashimoto’s is an autoimmune condition where the immune system attacks the thyroid. In these cases, the thyroid gradually becomes less efficient at making hormones. 

When thyroid hormone production drops, the body slows down and many key functions can be affected. Because symptoms typically develop gradually, it’s easy to miss the signs at first.

A common cause of increased thyroid hormone production is Graves’ disease, an autoimmune condition where the immune system overstimulates the thyroid gland. This leads to excess hormone output, causing the body’s processes to speed up.

Because symptoms may resemble stress or other conditions, hyperthyroidism can sometimes go unnoticed until it becomes more severe.

Thyroid Hormone Replacement Therapy for Low Levels

Symptoms related to low levels of thyroid hormone may appear slowly, but they still can have a big impact on daily life.

Thyroid hormone replacement therapy is the standard treatment for low thyroid hormone levels. It typically involves taking a daily dose of synthetic T4 (levothyroxine), which helps restore hormone levels and rebalance your metabolism. Some people may also need a combination of T4 and T3, depending on how their bodies convert the hormone. 

People who may benefit from thyroid hormone replacement include those with:

• Autoimmune hypothyroidism (like Hashimoto’s disease)

• Post-thyroid surgery or radiation therapy

• Congenital hypothyroidism

• Persistent low thyroid function confirmed by lab testing and symptoms

How to Increase Thyroid Hormone Naturally

If you're looking for ways to support healthy thyroid function naturally, there are several science-backed lifestyle strategies that may help—especially when combined with medical care when needed.

• Nourish your thyroid with key nutrients: The thyroid needs iodine to make hormones, while selenium and zinc help with hormone conversion and antioxidant protection. Eggs, seafood, Brazil nuts, and fortified dairy can all support this process.

• Manage chronic stress: Long-term stress may affect the hypothalamus-pituitary-thyroid (HPT) axis and blunt hormone production. Incorporating stress-reducing practices like mindfulness, exercise, and breathwork may help keep the system in balance.

• Prioritize high-quality sleep: Sleep is essential for hormone regulation across the board. Aim for seven to nine hours of restful sleep each night to support your endocrine system.

• Limit exposure to endocrine-disrupting chemicals: Certain compounds in plastics, pesticides, and personal care products may interfere with thyroid hormone production. Opt for cleaner products where possible, and avoid microwaving food in plastic containers.

While these steps can be helpful for overall thyroid support, they are not a substitute for thyroid hormone replacement therapy when clinically indicated. But they can complement medical treatment and help you feel your best.

Where Can I Learn More About Hormone Balance?

LifeMD can help you understand any health changes you may experience in your daily life associated with hormonal imbalances. The LifeMD Women’s Health Program offers compassionate, personalized care for women based on your individual needs and concerns.

With personalized hormone therapy, expert guidance, and support that fits your life, getting back to balance is more accessible than ever.

Join the waitlist today and take the first step toward feeling like you again.

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