Friday, August 19, 2022

What Is Thyroid Hormone Replacement

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To Optimize Levels Of Biologically Active T3 Combination Therapy With Bio

Thyroid Cancer: Thyroid Hormone Replacement. Research, When To Suppress TSH. Dr. Klopper.
  • Combined T4 and T3 therapy resulted in symptoms, well-being and weight loss in comparison with straight T4 therapy. A decrease in weight resulted from using higher T3 levels. Journal of Clinical Endocrinology and Metabolism 2005 May 90: 2666-74
  • Patients that took a combination of T4 and T3 experienced better mood, energy, concentration and memory and improved well-being. Patients on just T4 experienced no change. New England Journal of Medicine 1999 February 340:424-9

What Are The Uses For Thyroid Replacement Hormones

Thyroid replacement hormones are used to treat hypothyroidism and myxedema, a condition that is caused by prolonged hypothyroidism. Thyroid replacement hormones prevent thyroid hormone release from cancerous thyroid nodules and are used therefore to treat thyroid cancers. They also are used to manage thyrotoxicosis, a condition in which there are high levels of thyroid hormones resulting from over-active thyroid glands and too much thyroid hormone. Thyrotoxicosis may progress to hypothyroidism or cause the growth of goiters necessitating the use of thyroid replacement hormones.

What Are Thyroid Replacement Hormones And How Do They Work

Thyroid replacement hormones are medications used to treat hypothyroidism, a condition in which the production of thyroid hormone in the body is abnormally low. Thyroid hormones increase cellular metabolism that is 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 mediate. The thyroid gland, a gland found in the lower neck is responsible for the production of thyroid hormones. It produces two main hormones, thyroxine and triiodothyronine . The hormone responsible for most of the biological effects in the body is T3. When T4 is released into the blood by the thyroid gland, most of it is converted to T3 which is responsible for the cellular metabolic processes. Commercially available thyroid hormones are either natural or synthetic . Desiccated thyroid or thyroid extract , a natural thyroid hormone is derived from beef or pork. Levothyroxine sodium , is the synthetic version of thyroxine ,liothyronine sodium , is the synthetic version of tT3 andliotrix is a synthetic thyroid hormone containing a mixture of T4and T3.

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Thyroid Hormone Replacement For Hypothyroidism

It is controversial whether using combination therapy with T4 and T3 together may be helpful for some patients with ongoing symptoms that could be related to hypothyroidism. Some studies have suggested some improvement in symptoms in a subset of patients with hypothyroidism when treated with combination T4+T3 therapy, others have not. Unfortunately, the studies have generally been small, have used different dosing combinations of T4+T3, have not necessarily treated both groups to an equivalent TSH, and have had design issues that make them susceptible to bias. This leaves us in the position where there is no convincing evidence to suggest that combination therapy will help some patients with hypothyroidism who continue to feel unwell despite appropriate levothyroxine treatment. Also, there is no definite proof that combination treatment will not help some patients. Therefore, a trial of combination T4+T3 could be reasonable in some patients, but not all will benefit.

In order to more closely mimic normal human thyroid function a combination of levothyroxine and liothyronine can be used in doses selected to come close to the human ratio of T4:T3 production of about 15:1. Still the daily T3 dose of the treatment should be divided into 2-3 doses evenly spaced doses.

Deric Morrison MD FRCPCAssistant Professor, Division of Endocrinology, Dept. of MedicineUniversity of Western Ontario,St. Josephs Health CentreLondon, Ontario

Thyroid Hormone Receptors And Molecular Signaling In The Brain

What is Thyroid Hormone Replacement Therapy?

Thyroid hormones signal through nuclear thyroid hormone receptors THR- and THR- as both homodimers and heterodimers. Hormone-receptor complexes bind to thyroid hormone response elements in the promoter region of target genes, which are then transcribed ., In the brain, THR-1 is the most highly expressed nuclear thyroid receptor 70%80% of T3 binds to THR-1. Despite its widespread distribution in neural tissue, deletion of all of the thyroid hormone receptors in the brain does not produce a typical hypothyroid phenotype. This suggests that the lack of T3 has worse consequences than the lack of THRs It also supports thyroid hormone bioactivity that is not dependent on canonical thyroid hormone receptors.

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Are There Side Effects

Thyroid hormone replacement therapy often has a few side effects. While medications impact people in various ways, some of the most common issues result from overcorrection of common symptoms. Weight loss, overheating, anxiety, difficulty sleeping and irritability can occur after taking thyroid medication, which is often a result of being slightly overmedicated. If you find this to be the case, you can talk to your doctor about correcting your dosage or even switching to another prescription that doesnt cause the same side effects.

Challenges To Combination Therapy

These initial reports suggested that a change in the treatment for primary hypothyroidism should be considered. Consequently, a number of other investigators sought to confirm these findings . Throughout these papers are key differences in study design. In particular it is important to note the type of hypothyroidism in the study population and the time period for different treatments. We therefore provide a high level of detail necessary to allow the reader to adequately compare the various reports.

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How Is Thyroid Hormone Replacement Therapy Dosage Determined

Healthcare providers do careful blood testing to find the proper dose of hormone replacement therapy for each person. The blood tests reveal levels of thyroid hormones in the blood, as well as thyroid-stimulating hormone released by the pituitary gland. The pituitary gland plays an integral role in the functioning of the thyroid gland. It controls how much thyroid hormone is released by making TSH that “stimulates” the thyroid. Increased levels of TSH may indicate that you have an underactive thyroid or that thyroid hormone replacement needs to be increased.

You will have lab tests to measure levels of thyroid hormones and TSH. Hypothyroidism can be a progressive disease. This needs dosage increases over time.

To make sure that your thyroid hormone replacement works properly, consider the following recommendations:

  • Maintain regular visits to your healthcare provider.

  • Take your thyroid medicine at least 1 hour before breakfast and any calcium or iron medicines you may take. Or take at bedtime, or at least 3 hours after eating or taking any calcium or iron medicines.

  • Tell your healthcare provider of your thyroid hormone treatment before beginning treatment for any other disease. Some treatments for other conditions or diseases can affect the dosage of thyroid hormone therapy.

  • Let your healthcare provider know if you become pregnant.

  • Tell your healthcare provider of any new symptoms that may arise.

  • Tell all healthcare providers of your thyroid condition and medicine dosage.

Should I Take Thyroid Hormone While I Am Pregnant

Thyroid Hormone Replacement

Since thyroid hormone is a hormone normally present in the body, it is absolutely safe to take while pregnant. Indeed, it is very important for pregnant women, or women who are planning to become pregnant, to have normal thyroid function to provide the optimum environment for her baby. Women who are taking thyroid hormone often need an increased dose of thyroid hormone during their pregnancy, so it is important to have thyroid hormone and TSH levels measured once you know that you are pregnant. You should discuss the timing of thyroid blood tests with your physician, but often thyroid function is checked at least every trimester.

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History Of Treatment For Hypothyroidism

Historically, before thyroid hormones were identified, patients with hypothyroidism were treated with ovine thyroid gland extracts. Thyroxine was isolated in 1914 and became clinically available several decades later. Since the 1930s, T4 became the therapy of choice for hypothyroidism. Synthesis of T3 during the 1950s led to the development of combination therapy, which was first used clinically during the 1960s. It was later found that T4 is converted to T3 through peripheral deiodination and that an excess of T3 leads to hyperthyroidism introducing an entirely different set of symptoms . In addition to avoiding the risk for hyperthyroidism, T4 monotherapy is widely used because of its long half-life of compared to only 2.5 days for T3. The short half-life of T3 results in peak serum levels within 24 hours following oral administration and accordingly the need for relatively frequent dosing. With effective peripheral conversion, a low risk of hyperthyroidism, and less frequent dosing, T4 is widely considered a much more convenient and effective therapy for patients.

Tips For Taking T4 Medicines

  • Take your T4 medicine at the same time every day to get into a routine. Take it on an empty stomach with a glass of water and wait 30 minutes before eating.
  • Store medicines in the fridge to maintain the T4 level in the tablets. If you are travelling, the medicine will last up to 30 days without refrigeration. Some T4 medicines do not need refrigeration check with your doctor or pharmacist.
  • If you miss a dose, you should usually take it as soon as you remember. But if its almost time to take the next dose, skip the dose you missed.
  • Wait two hours before taking calcium or iron supplements as these affect the stomachs ability to absorb the T4.
  • Check with your doctor if its safe to continue taking other medicines or supplements.
  • Tell your doctor if you are pregnant or are planning to get pregnant, as you may need to take a higher dose.
  • Dont stop taking the T4 medicine without discussing it with your doctor.

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Desiccated Porcine Thyroid Medication

Desiccated animal thyroid extract was an early way to treat hypothyroidism.

This is a powder for medical use. It is also a combination of T3 and T4 hormones.

Common brands of this NDT include:

  • Acella NP Thyroid
  • WesThroid
  • WP Thyroid

This type of levothyroxine alternative contains a higher concentration of the T3 to T4 ratio. Therefore, taking too much can lead to excessive thyroid hormone production.

Are Thyroid Drugs Safe


Thyroid medicines are safe when taken at the recommended dose and prescribed by a doctor. You must ONLY take what your doctor recommends. The correct dosage for you is based on your age, health, current natural thyroid hormone levels, and weight.

When you first start treatment for hypothyroidism, your doctor will regularly monitor the levels of different thyroid hormones in your blood to determine if your dosage of thyroid medication needs adjusting. Once the correct dosage has been established for you, the frequency of these blood tests will decrease. Thyroid drugs are generally taken for life.

It will take a few months for your thyroid levels to get back to normal but as long as you are taking your thyroid drugs as prescribed, then you should not have many side effects. Side effects generally happen because you are taking too much thyroid hormone.

Thyroid hormones should NEVER be taken by people without thyroid problems to treat obesity or for weight loss. Some fatalities have occurred when they have been used if these drugs are taken in large dosages for this indication.

Also, talk to your doctor about your diet. Some people with hypothyroidism are particularly sensitive to the effects of iodine, and it may trigger or worsen hypothyroidism. In addition, high fiber diets and certain types of foods such as soy or cruciferous vegetables may affect how your body responds to thyroid drugs.

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Dosage Or Drug Quality Issues

Overmedication may occur when there is an error in dosage. For example:

  • Your healthcare provider may prescribe a dosage that is too high for you.
  • Your pharmacist may give you the wrong dosage or incorrect instructions for use.

It is also possible that the quality of your medication may change from one refill of your prescription to another. This is sometimes the case when your medication is produced by several different manufacturers.

If you are taking generic levothyroxine, you may receive a batch of medication that is more or less potent than your previous refill. Even a slight change of potency from one refill to the next can lead to hypothyroidism.

Switching formulations of levothyroxinefor example, from tablet to gel-caps or liquidcan also cause overmedication. That’s because your body absorbs certain formulations of levothyroxine better than others.

In particular, both Tirosint liquid gel-caps and Tirosint-SOL liquid levothyroxine absorb better than levothyroxine in tablet form. You may be prescribed gel-cap or liquid levothyroxine if you are allergic to dyes or fillers, but the switch may result in overmedication.

This is why close monitoring is important. You should get your TSH level checked within six weeks after beginning thyroid hormone replacement, or after changing the brand or dose of your medication.

Pay particular attention to symptoms that develop after a recent pharmacy refill. They may be due to a medication error or change in the formulation.

Thyroid Hormone Replacement Therapy For Thyroid

Surgery can be used to treat papillary and follicular thyroid cancers, medullary thyroid cancer and sometimes anaplastic thyroid cancer. If you have all of your removed, you will need to take thyroid hormone replacement tablets every day for the rest of your life.

You may have to take thyroid hormone replacement tablets even if you had just part of your thyroid gland removed. Thyroxine is the most common drug given.

Thyroid hormone tablets have 2 functions:

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Thyroid Hormone Replacement Dosage

The correct dosage of thyroid hormone medication is crucial for you to maintain the proper hormonal balance. For this, your doctor will run careful blood testing to determine the suitable dose for your therapy.

The blood tests usually reveal thyroid hormonal levels and the amount of TSH released by the pituitary. An increased level of TSH indicates that you have an underactive thyroid, and thus your doctor will increase your replacement hormone. In addition, to determine the correct dose, the provider will check your age, weight, and medical history along with a physical examination.

The medication usually takes some time to adjust. Your doctor will check your blood levels in six months to determine if you need an increased dose. People with coronary artery disease initially have a smaller amount of medication, and gradually, the dosage increases. It will allow your heart to adjust to the increased metabolism.

Thyroid replacement medications like levothyroxine are readily available in the shops and inexpensive. However, if you need to change the brand or are unavailable, inform your doctor to ensure the correct dosage.

What Else Can You Do

THYROID THURSDAY – Thyroid Hormone Replacement Options

While thyroid hormone replacement therapy and other forms of medical intervention are great for treating issues head-on, you can also make smart lifestyle choices to aid in the healing and wellness process.

While healthy living isnt a replacement for taking the medications you need, it can help your body utilize hormone therapy to its fullest. Getting enough sleep, exercising regularly, drinking plenty of water and eating a healthy diet are great ways to go about this. Specifically, eating a more Mediterranian diet rich in vegetables and fruits, getting moderate exercise and cutting down on processed foods are lifestyle changes that often help support healthy thyroid function.

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The Role Of Circulating T3 Is Unclear

Circulating T3 appears to have a different role in physiology than circulating T4. This is illustrated by several observations, some familiar to endocrinologists and some less familiar. First, even during profound hypothyroidism , T3 is almost always maintained in the reference range. Second, by contrast, during acute illness T3 falls rapidly whereas T4 is maintained, or may even rise . Third, 25% of children under 7 years of age have T3 levels above the adult reference range, with a normal TSH . Fourth, higher T3 levels in children correlate with increased body mass index . Consistent with this, children with higher T3 levels have earlier onset of puberty . Mendelian randomization studies suggest that in fact fat mass somehow causes an increase in T3 levels, rather than vice-versa . Taken together, these observations suggest that circulating T3 levels have a role in signaling nutritional or health status to the brain, perhaps more so than being a major source of T3 to tissues.

Why All The Fuss About The Thyroid

When a person has hypothyroidism, or an underactive thyroid , their thyroid gland doesnt produce enough hormones for the bodys needs. This affects their metabolism and how their body uses energy.

It can ultimately result in symptoms, such as:

  • Fatigue
  • Insomnia
  • Muscle aches

Key Insight: Hypothyroidism is the main reason women are prescribed thyroid replacement therapy. This often means taking thyroxine , a precursor to active thyroid hormone and triiodothyronine , the active form of thyroid hormone.

These hormones regulate the energy level of every cell in your body. If there is not enough being produced naturally, it can affect how fast your body burns calories, how rapidly you can think and how fast your heart beats.

Concerned about your thyroid? Heres a great place to start

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What Is Thyroid Hormone Replacement

There is one purpose for taking thyroid hormone: to replace the thyroid hormone levels when your thyroid is underactive .


L-thyroxine is the most commonly used form of thyroid hormone replacement.

  • This medicine contains the synthetic form of a thyroid hormone
  • L-thyroxine as medication is identical to the L-thyroxine, which is the major hormone made by the thyroid gland
  • L-thyroxine is the most commonly prescribed form of thyroid hormone replacement

Initial L-thyroxine dose

L-thyroxine is taken once each day by mouth

  • Stable blood levels of thyroid hormone are achieved when L-thyroxine is taken at approximately the same time each day, ideally the first thing in the morning on an empty stomach.
  • Avoid taking food within 1 hour and avoid calcium, iron sucralfate, aluminum-containing antacid, and multivitamins within 2 hours before or after the dose.
  • If a dose is skipped, two doses may be taken the following day.

Blood levels of thyroid stimulating hormone should be checked approximately 4-6 weeks following each adjustment of LT4 dose.

  • L-thyroxine comes in oral forms, for patients to use at home, and intravenous forms used in a hospital setting.

L-thyroxine during pregnancy and breastfeeding:

  • It is safe to take L-thyroxine during pregnancy.
  • The dose of L-thyroxine often must be increased during the first 20 weeks of pregnancy. TSH testing is recommended immediately after pregnancy is confirmed.

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