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Side Effects of thyroid hormone products



Thyroid Hormone Replacement Drugs

When your thyroid is either underactive, non-functioning, or has been all or in part surgically removed, you are considered hypothyroid. 

The conventional treatment for hypothyroidism is thyroid hormone replacement -- basically, taking a prescription a drug that acts similarly in the body to the human hormone thyroxine that the thyroid would normally produce.

Levothyroxine/Synthetic T4

The vast majority of doctors prescribe the synthetic drug known as levothyroxine for thyroid hormone replacement. The most commonly known brand of levothyroxine is Synthroid. There's also Levoxyl, Levothroid, Unithroid, and many brands outside the U.S. In addition, there are "generic" versions of the T4 drugs, but many doctors do not recommend them. Studies have shown the brand name levothyroxine drugs in the U.S. to be bioqeuivalent, meaning that they accomplish the same thing from a medical standpoint Different brands, however, have different fillers, and a small number of patients apparently are allergic to the fillers in one versus another. Levothyroxine provides a synthetic version of one hormone, thyroxine, known as T4. Some people with hypothyroidism find that levothyroxine therapy is sufficient treatment for their hypothyroidism.

Liothyronine/Synthetic T3

Some doctors treat hypothyroidism using levothyroxine, plus an additional drug, liothyronine (brand name, Cytomel), or prescribe it in a time released compounded version. Liothyronine is a synthetic version of triiodothyronine, abbreviated as T3, the active thyroid hormone in the body. In a person with normal health and thyroid function, the thyroid produces mainly T4 and some T3, and the T4 is converted to T3, which is then the active hormone used by the body's cells. Some doctors and endocrinologists use supplemental T3. This was supported in research featured in the New England Journal of Medicine, but some researchers in 2003 have also claimed it to be ineffective. There is still a belief by some practitioners that patients do not need T3, because they will convert T4 into the T3 the body needs. The alternative medical community believes that impaired conversion of T4 to T3 may create a deficiency in T3 that warrants direct T3 supplementation.

Liotrix / Synthetic T4/T3 Combination

The synthetic T4/T3 combination drug is liotrix, brand name Thyrolar. This drug is not very regularly prescribed, but is preferred by some physicians who wish to provide both T4 and T3, but prefer a synthetic drug.

Natural Thyroid

Natural thyroid is dessicated thyroid, derived from the gland of pigs. It was the standard thyroid drug until levothyroxine came on the market in the second half of the 20th century. Some doctors, more often osteopaths, naturopaths, and holistics M.D.s, are in favor of these natural drugs, because they believe that since the drug contains a full spectrum of thyroid hormones, beyond just the T4 and T3, it most closely mimics the human thyroid hormone. The most popular brand of natural thyroid is Armour thyroid.



Levothyroxine Side Effects

Possible Levothyroxine Side Effects

As with any medication, levothyroxine can cause allergic reactions. Seek medical attention immediately if you develop any signs of an allergic reaction, including:


·  Wheezing or difficulty breathing

·  An unexplained rash

·  Hives

·  Itching

·  Unexplained swelling (especially of the lips, mouth, or throat).


Levothyroxine side effects typically occur when the dosage is too high. Too much levothyroxine can cause symptoms of hyperthyroidism (an excess of thyroid hormones). Because hyperthyroidism can be quite dangerous, any of these symptoms should be reported to your healthcare provider, as they may signal that your levothyroxine dosage needs to be decreased. These side effects may include:


·  Feeling hot all the time and increased sweating

·  Fever

·  An increased appetite, along with weight loss

·  Heart palpitations

·  A rapid heart rate (tachycardia)

·  Heart failure, chest pain, or a heart attack

·  Difficult or painful breathing

·  Insomnia (see Levothyroxine and Insomnia)

·  Emotional changes

·  Hair loss (see Levothyroxine and Hair Loss)

·  Flushing

·  Broken bones or other signs of weakened bones

·  Menstrual problems or fertility problems

·  Shakiness (tremors) or muscle weakness

·  Hyperactivity, nervousness, anxiety, or irritability

·  High blood pressure (hypertension)

·  Diarrhea, vomiting, or abdominal cramps (stomach cramps)

·  Seizures.

You should report any levothyroxine side effect to your healthcare provider right away, as it may be a symptom of hyperthyroidism and an indication that your levothyroxine dosage is too high. Also, seek immediate medical attention if you notice any signs of an allergic reaction while taking levothyroxine.



Comments from Dr. Martin Wang:

(1). It is so common that once patient complain chronic fatigue, and if the blood level of T4 is low, doctors are so ready to give levothyroxine to patient, with the hope to increase the physical energy for the patients. Doctors seem never search other reasons that may contribute to the tiredness feeling of the patients. They do not care if the application of artificial thyroid hormone-similar products for a long time will have what kind of disadvantage to the patients.

Similar to any hormones in the body, such as insulin, estrogen and others, one of the reverse feedback regulation for the production of the hormone by the corresponding hormone producing glands is their products. This means, if you have more insulin in the blood, the insulin will prevent more production of insulin by the pancreas. Similarly, if you have more thyroid hormone in the blood, it will pass signal to the thyroid gland and makes the gland to produce less thyroid hormone to release into the blood.

So, if we increase the thyroid hormone level by application of levothyroxine, the thyroid gland may “feel” that there is enough thyroid hormone in the blood so do not work hard to produce more thyroid hormone. After a long time, it’s hormone producing cells may “shrink” and lose its ability to produce more thyroid hormone. This is why it could be difficult to quit the levothyroxine when it has been used for a long time.

(2). It is hard in clinic for western medical doctor to identify the exact reasons that contribute to the tiredness feelings of patients and the reasons that cause the lower blood level of thyroid hormone. I know it is difficult but doctors should be care for the prescription of levothyroxine. Prescribe it when it is definitely needed. For example, if the whole thyroid glands have been removed by surgery for the treatment of thyroid cancer. Whenever there is even a part of the thyroid cells in the glands, try not to disturb it. Doctor should try to solve the chronic fatigue by other means.

(3). To us, to use the levothyroxine for the treatment of chronic fatigue is as to use gun to shoot mosquito. It does not touch the point and waste the medicine.

The application of the Traditional Chinese Medicine is a very promising means to solve the chronic fatigue. In my experience, it is as easy as to solve depression and anxiety in patients. It is usually only needed for several weeks (usually within one week), the chronic fatigue and emotional disorders can be much improved. So, always try the no harm therapy before starting something that may need you to take for years even for ever.


Regulation of Thyroid Hormones

The thyroid gland concentrates iodine that the body absorbs from various foods to make thyroid hormones. The thyroid gland makes mostly T4. Very little T3 is made by the thyroid gland. The liver and other organs convert T4 into T3. Certain diseases and drugs can affect the conversion of T4 into T3.

Both T4 and T3 circulate in the blood, mostly bound to certain proteins. Thyroid hormones become active in their role of controlling the speed of vital body functions when they are freed from protein binding. The body regulates a balance between bound thyroid hormones and free thyroid hormones.

Through a complex interaction between the hypothalamus (a part of the brain) and the pituitary gland (located inside the skull, just underneath the brain), the thyroid gland knows how much of its hormones to produce. The hypothalamus makes thyrotropin-releasing hormone, which then stimulates the pituitary gland. The pituitary gland responds by making another hormone called thyroid-stimulating hormone, or TSH. As the name suggests, thyroid-stimulating hormone stimulates the thyroid gland to make hormones. If the level of thyroid hormones in the blood climbs above what is needed, the pituitary gland makes less thyroid-stimulating hormone. The thyroid gland then cuts back on making thyroid hormones. If the level of thyroid hormones in the blood falls too low, the pituitary gland makes more thyroid-stimulating hormone. In response, the thyroid gland makes and secretes more thyroid hormones. The body adjusts the amount of thyroid hormones to suit its needs in the same way a thermostat adjusts the temperature in a house.


Thyroid Problems Overview

The thyroid gland is located on the front part of the neck below the thyroid cartilage (Adam's apple). The gland produces thyroid hormones, which regulate body metabolism. Thyroid hormones are important in regulating body energy, the body's use of other hormones and vitamins, and the growth and maturation of body tissues.

Diseases of the thyroid gland can result in either production of too much (hyperthyroidism) or too little (hypothyroidism) hormone.

*       Production of thyroid hormones: The process of hormone synthesis begins in a part of the brain called the hypothalamus. The hypothalamus releases thyrotropin-releasing hormone (TRH). The TRH travels through the bloodstream to the pituitary gland, also in the brain. In response, the pituitary gland then releases thyroid-stimulating hormone (TSH) into the blood. The TSH then stimulates the thyroid to produce the two main thyroid hormones, L-thyroxine (T4) and triiodothyronine (T3). The thyroid gland also needs adequate amounts of dietary iodine to be able to produce T4 and T3.

*       Regulation of thyroid hormone production: To prevent the overproduction or underproduction of thyroid hormones, the pituitary gland can sense how much hormone is in the blood and adjust the production of hormones accordingly. For example, when there is too much thyroid hormone in the blood, the TRH does not work effectively to stimulate the pituitary gland. In addition, too much thyroid hormone will prevent the release of TSH from the pituitary gland. The sum effect of this is to decrease the amount of TSH released from the pituitary gland, resulting in less production of thyroid hormones in the thyroid gland. This then works to restore the amount of thyroid hormone in the blood to normal. Defects in these regulatory pathways may result in hypothyroidism or hyperthyroidism.