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May 02, 2023 5 min read

For millions of people across the globe, hypothyroidism, or an underactive thyroid, is a reality that affects their daily lives. A common treatment option for hypothyroidism is the use of thyroid hormone replacement therapy, which typically consists of bioidentical hormones. But what is it? And are there any risks to using it? Here's what you need to know.

Thyroid hormone physiology

Before delving into bio-identical hormones, it's important to have a clear understanding of thyroid hormone physiology. The human thyroid gland produces two main thyroid hormones: T4 (thyroxine) and T3 (triiodothyronine). The gland mostly makes T4, with a smaller amount of T3.

T4 is the inactive form of thyroid hormone, which enters your cells and undergoes a conversion process to become T3, the active form. T3 is the hormone that actually affects our body. It's responsible for regulating metabolism, thus playing a pivotal role in our overall health and well-being. The ratio of T4 to T3 produced by the human thyroid gland is approximately 14:1.

What are bioidentical thyroid hormones?

Bio-identical hormones are synthetic hormones that closely resemble the hormones naturally produced by the human body. They are used as a treatment for individuals who have low or imbalanced hormone levels. Examples of bioidentical hormones include menopausal hormone therapy, which helps alleviate menopausal symptoms, and thyroid hormone replacement therapy, which addresses hypothyroid symptoms.

The one specifically used for thyroid hormone replacement therapy is called bio-identical thyroid hormones. These hormones are chemically identical to the hormones naturally produced by the human thyroid gland. In other words, they are exact replicas of the natural thyroid hormones, so they can function similarly within the human body. That's why they are often prescribed to treat hypothyroidism - they help fill the gap when your body isn't making enough thyroid hormone. This helps improve your energy levels, manage weight, and get rid of other symptoms.

There are various different forms of bio-identical hormones available. Some prescription forms are premade by drug companies. You can find FDA-approved bioidentical hormones, as well as over-the-counter and custom-compounded bioidentical hormones.

Both FDA-approved and compounded bioidentical hormone therapy comes in various doses and forms, including tablets and capsules.

Are levothyroxine and natural desiccated thyroid (NDT) bioidentical?

Although levothyroxine and natural desiccated thyroid (NDT) are different, they are both considered bioidentical hormones.

Levothyroxine: A bio-identical T4 Hormone

Levothyroxine is a synthetic thyroid hormone that is chemically identical to the T4 hormone produced by the thyroid. It's the standard treatment for hypothyroidism and is considered bio-identical. Levothyroxine is available in various forms, including tablets, capsules, and liquid solutions. The dosage of this thyroid medication is typically adjusted based on blood tests that measure the levels of thyroid-stimulating hormone (TSH), which helps determine the body's need for thyroid hormones.

Although levothyroxine is a bioidentical thyroid hormone, it primarily supplies the body with T4, which is a pro-hormone. This means that it needs to be converted into T3, the active form of thyroid hormone, for it to be utilized by the body. While this conversion process works well for most people, some individuals may have difficulty converting T4 to T3 in sufficient quantities to meet their body's needs. In such cases, treatments that contain a combination of T4 and T3, such as natural desiccated thyroid (NDT), may be more suitable.

Natural desiccated thyroid (NDT): A more comprehensive bio-identical hormone option

NDT is derived from the dried thyroid glands of pigs or cows and contains all the bioidentical thyroid hormones, including T4, T3, T2, and T1. It has been used for over a century to treat hypothyroidism and was the standard treatment before the development of synthetic T4 (levothyroxine) in the 1950s. NDT can be obtained through prescription medications, such as Armour Thyroid and NP Thyroid, as well as in the form of NDT supplements like VitaliThy. The NDT supplement VitaliThy is available to buy online.

Advocates of NDT argue that it provides a more comprehensive thyroid hormone replacement therapy compared to levothyroxine, as it supplies the body with all the bioidentical thyroid hormones, not just T4. Some studies have shown that patients with hypothyroidism who are treated with NDT experience better symptom relief and higher satisfaction levels compared to those treated with levothyroxine.

What are the uses of bioidentical hormones?


The primary use of bioidentical thyroid hormones is in the treatment of hypothyroidism. Patients who do not respond well to synthetic hormone therapy or continue to experience symptoms despite adequate hormone levels may benefit from switching to bio-identical hormones.

Hashimoto's thyroiditis

Bio-identical hormones may help alleviate symptoms associated with Hashimoto's thyroiditis, such as fatigue, weight gain, and mood swings, by providing a more natural hormone balance.

Post-thyroidectomy and radioactive iodine therapy

Individuals who have undergone thyroidectomy (surgical removal of the thyroid) or radioactive iodine therapy for hyperthyroidism may require lifelong thyroid hormone replacement therapy. In these cases, bio-identical hormones can be a suitable option.

Other uses

Occasionally, bio-identical thyroid hormones may be prescribed for patients with thyroid hormone resistance, a rare condition in which the body does not respond appropriately to thyroid hormones. In such cases, higher-than-normal doses of thyroid hormones may be required to achieve the desired therapeutic effect.

Are bioidentical thyroid hormones safe?

Bioidentical thyroid hormone replacement therapy is generally considered safe when taken at the appropriate dosage and under the guidance of a healthcare professional. However, like any medication, there may be potential side effects or risks involved.

1. Overdose

Taking too much thyroid hormone can lead to symptoms of hyperthyroidism, which include headache, nervousness, irritability, sweating, increased appetite, or changes in menstrual periods. These side effects are usually mild and can be managed by adjusting the dose, changing the medication's form, or addressing any underlying conditions that may be contributing to the symptoms.

2. Allergic reactions

Some individuals may experience allergic reactions to the ingredients in NDT or levothyroxine. Symptoms may include rash, itching, swelling, or difficulty breathing. If you suspect an allergic reaction, contact your healthcare provider immediately.

3. Drug interactions

Certain medications, such as calcium or iron supplements, can interfere with the absorption of thyroid hormones. Be sure to discuss all medications and supplements you are taking with your healthcare provider to avoid potential interactions.

4. Pregnancy and breastfeeding

Thyroid hormones are essential for the proper development of a fetus, so it is crucial to maintain appropriate levels during pregnancy. If you are pregnant or breastfeeding, discuss your thyroid hormone treatment with your healthcare provider to ensure the safety of both you and your baby.

Are there contraindications to bioidentical thyroid hormone?

Are there situations where bioidentical thyroid hormones should not be used? Yes, individuals with specific medical conditions, such as uncontrolled adrenal insufficiency or untreated hyperthyroidism, should avoid using bio-identical thyroid hormones. Always consult your healthcare provider before starting any new medication or treatment.

How important is monitoring while on bioidentical thyroid hormone?

Regular monitoring of thyroid hormone levels is essential while on bio-identical hormone therapy. This ensures that the dosage is adjusted as needed to maintain optimal hormone levels and prevent potential complications.

Conclusion: Bioidentical thyroid hormones are a great help for people with hypothyroidism

Bioidentical thyroid hormones, including levothyroxine and natural desiccated thyroid (NDT), play a critical role in the treatment of hypothyroidism. While levothyroxine is a bioidentical hormone that only supplies the body with T4, NDT offers a more comprehensive hormone replacement option by providing T4, T3, T2, and T1.

Both treatments have their merits and drawbacks, and the choice of therapy depends on various factors, including the individual's unique needs, preferences, and response to treatment. If you have hypothyroidism or suspect that you might have a thyroid problem, consult a healthcare professional to discuss the most appropriate treatment options for your situation.

If you want to try a more natural approach, VitaliThy, a natural desiccated thyroid you can buy online, is a great choice.

Wojciech Majda
Wojciech Majda

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