Thyroid Replacement Therapy (THRT)

Thyroid replacement therapy is a hormone-based therapy used to treat hypothyroidism, a condition in which the production of thyroid hormone in the body is abnormally low. Thyroid hormones are used to increase the activity of cells responsible for growth, development of tissues, maintenance of brain function, body temperature regulation, and several other cellular processes.

Low levels of thyroid hormones in the body can result in many problems, given the numerous activities that they impact. 

Understanding Thyroid Problems

The thyroid gland is a butterfly-shaped endocrine gland that is normally located in the lower front of the neck. The thyroid’s job is to make thyroid hormones, which are secreted into the blood and then carried to every tissue in the body. Thyroid hormone helps the body use energy, stay warm, and keep the brain, heart, muscles, and other organs working properly.

There are different types of thyroid problems. The two primary types of thyroid issues are an overactive thyroid (known as hyperthyroidism) and an underactive thyroid (known as hypothyroidism). 

People struggling with thyroid issues experience symptoms that include:

  • Weight gain and loss
  • Fluctuating energy levels
  • Memory and cognition issues
  • Changes in moods, skin, nails, hair, and bowel habits


Hypothyroidism, or an underactive thyroid gland, is by far the most common thyroid issue. Five out of every 100 adults has hypothyroidism, although most cases are mild and exhibit few symptoms. 

The disorder tends to affect women more than men. Hypothyroid symptoms come on slowly as the thyroid gland produces fewer and fewer of the hormones necessary to keep the metabolism operating effectively. 

In the earliest stages of the disease, few patients notice symptoms, as the symptoms seem like the normal side effects of stress. However, over time, symptoms like weight gain and fatigue can quickly add up and contribute to the development of serious health issues including obesity, infertility, and joint pain.

The most common symptoms of hypothyroidism include:

  • Fatigue
  • Unexplained weight gain
  • Constipation
  • Dry skin and hair
  • Hair Loss
  • Puffiness or swelling in the face
  • Muscle aches and weakness
  • Heavy menstrual periods
  • Brittle hair and nails
  • Depression
  • Cold intolerance


When the thyroid produces too many hormones, this is known as an overactive thyroid (or hyperthyroidism). The condition is more common in women than men and is more likely to be diagnosed over the age of 60. It is often caused by an autoimmune disorder known as Graves’ disease.

Failure to treat hyperthyroidism can result in an increase in metabolic rate, which leads to undesirable symptoms. 

Symptoms of hyperthyroidism include:

  • Frequent heart palpitations
  • Sweating, anxiety
  • Weight loss
  • Heat intolerance
  • Muscle weakness

Patients with heart disease and diabetes are at a greater risk of complications associated with an overactive thyroid. 

Radioactive iodine and anti-thyroid medications are the most common ways to treat hyperthyroidism. Removing the thyroid gland via surgery (known as a thyroidectomy) is another option, although that is usually done when other options have been proven unsuccessful.

How Thyroid Replacement Therapy Works

Thyroid hormone replacement therapy is unique compared to most medications as it aims to substitute a deficient hormone. The primary objective of this therapy is to closely mimic normal thyroid function.

The thyroid hormone, levothyroxine is bioequivalent to the body's own hormone, thyroxine (T4), and is typically available in tablet, gel capsule, or liquid forms.

Safety concerns mainly revolve around dosage, with the risk of taking too much or too little. Regular monitoring of thyroid function by a physician is crucial to maintaining optimal hormone levels.

When prescribed thyroid hormone replacement therapy, the goal is to compensate for the lack of natural hormone production. In most cases, a daily oral dose of T4 (or a combination of T3 and T4) is recommended.

In the United States, the following thyroid replacement hormones are available:

  • Levothyroxine sodium (Levothroid, Levoxyl, Synthroid, Tirosint, Unithroid)
  • Liothyronine sodium (Cytomel, Triostat)
  • Liotrix (Thyrolar)

Hormone Replacement as a Treatment for Thyroid Cancer

Following surgery for differentiated thyroid cancer, hormone replacement therapy is essential to compensate for the removed thyroid gland's function and to hinder the growth of thyroid cancer cells.

Thyroid hormone suppression therapy plays a pivotal role in treating thyroid cancer by effectively impeding the growth of residual or microscopic thyroid cancer cells. Patients in this scenario typically require a higher dose than usual for replacement, as the benefits of preventing cancer cell growth outweigh the associated risks.

While higher doses may slightly elevate the risk of rapid heart rhythms, insomnia, or reduced bone density, close physician monitoring allows for necessary adjustments to be made. The duration of suppression therapy varies based on the cancer's status.

Thyroxine (T4) halts the production of thyroid-stimulating hormone (TSH), which not only stimulates the thyroid to produce hormones but can also promote the growth of thyroid cancer cells.

If you have had your thyroid gland removed, you will be given thyroxine at a slightly higher dose. This helps to reduce the risk of the cancer coming back after surgery. This is called TSH suppression and is part of your ongoing treatment.

Tailoring your Thyroid Replacement Therapy

When you start taking thyroid hormone, the initial dose is carefully selected based on information such as your weight, age, and other medical conditions.

The dose may need to be adjusted periodically by your physician to keep your thyroid levels normal. Your physician will make sure the thyroid hormone dose is correct by performing periodic physical examinations and checking your TSH levels.

Testing for Thyroid Disorders

When it comes to checking for thyroid issues, it's common to undergo thyroid function tests because the symptoms often match those of a thyroid disorder.

Sometimes, even if you're told that your lab results are "normal," they might not be in the best range for you. This is because what's considered normal can be broader than what's actually best for your health.

In traditional medical practice, a blood test for thyroid disorders usually only checks TSH levels and may not use the most up-to-date benchmark levels for that hormone.

While high TSH levels can indicate low T3 and T4 levels, high cortisol levels can actually lower TSH. If the levels of T3 and T4 aren't directly checked, you might have hypothyroidism without realizing it. 

At RBI Concierge Medicine, we understand how to test your thyroid levels correctly and see if you are being impacted by a thyroid disorder. 

What to Expect During Your Thyroid Replacement Therapy

Because thyroid hormone remains in your system for an extended period, taking it once a day ensures consistent levels of thyroid hormone in the bloodstream. 

When thyroid hormones are used to treat hypothyroidism, treatment aims to keep thyroid function within the same range as a person without thyroid problems. This is done by keeping the TSH level within the normal range. 

The best time to take thyroid hormones is typically on an empty stomach, first thing in the morning. This is because food in the stomach can affect the absorption of thyroid hormone. If you are taking several other medications, you should discuss the timing of your thyroid hormone dose with your physician. 

As an alternative, taking your thyroid hormone at bedtime can make it simpler to prevent your thyroid hormone from interacting with food or other medications.

Overall, the most important thing is to be consistent and take your thyroid hormone in the same way every day.

Do not stop your thyroid hormone without discussing this with your physician. Most thyroid problems are permanent; therefore, most patients require thyroid hormone for life. 

It is very important that your thyroid hormone and TSH levels are checked at least annually, even if you are feeling fine so that your thyroid hormone dose can be adjusted if needed.

Thyroid Replacement Therapy Side Effects

Thyroid replacement hormones usually are well tolerated, with side effects not being that common. If one does experience side effects, they usually include the following: 

  • Overdose: Excessive levels of thyroid hormone can lead to symptoms such as rapid or irregular heartbeat, sweating, nervousness, and irritability.
  • Osteoporosis: Prolonged use of high doses of thyroid hormone can contribute to weakened bones.
  • Other symptoms: These may include fatigue, diarrhea, heat sensitivity, sleep disturbances, high blood pressure, anxiety, depression, weight loss, and menstrual irregularities in women.

It's important to note that not everyone experiences these side effects, and they can vary based on individual health conditions and the specific dosage of thyroid hormone replacement therapy. 

That is why we continually monitor your thyroid levels, and adjust your medication as appropriate. 

Thyroid Replacement Therapy in Vero Beach, FL

At RBI Concierge Medicine, we offer comprehensive solutions for hormonal imbalances in women and men. Begin your journey towards wellness today with the guidance of our expert providers.

To schedule an appointment, call us at 772-492-6973 or contact us through our online form.

In Partnership with RBI
3730 7th Terrace, Suite 301
Vero Beach, FL 32960
(772) 492-6973
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