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Richard Haber, Mt. Sinai School of Medicine Melissa D. Katz, MD, Weill Medical College of Cornell University
The thyroid is a small butterfly-shaped gland that wraps around the windpipe in the front of the neck, and plays a critical role in the body's metabolism. Metabolic disorders occur when the thyroid secretes too little or too much thyroid hormone, and these disorders can affect almost every aspect of health.
Hypothyroidism is a very common condition among women in which the amount of thyroid hormone in the body drops below normal levels. One treatment strategy involves replenishing the body with a synthetic hormone called levothyroxine. How effective is it? And how do the various formulations differ? Below, two experts in the treatment of thyroid disorders discuss medications for this common condition.
How do you treat hypothyroidism?
MELISSA KATZ, MD: Women are the most commonly affected by this condition, and most of them respond very well to treatment with levothyroxine.
What is levothyroxine?
RICHARD HABER, MD: Levothyroxine, or thyroxine, is the naturally occurring hormone that the thyroid gland secretes. It's the principle form of thyroid hormone secreted by the thyroid gland. For those people who don't make thyroid hormone naturally, the drug form of levothyroxine can be used as a replacement. You can get levothyroxine from natural sources, which is comprised of animal thyroid gland that's been ground up and dried. That's the oldest way to do it and this method goes back to the 19th century. The same molecule can be synthesized by chemists. The synthetic drug is currently the way the best selling preparations are made. But the molecule thyroxine, whether synthesized in a chemistry laboratory or extracted from animal thyroid glands, is the same.
A lot of people, when they hear the word "synthetic", immediately think that somehow it's not as effective or it carries some harm and that natural is better. But the point you're making is that a molecule is a molecule.
RICHARD HABER, MD: Right.
How would you compare the purity of hormone in natural vs. synthetic products?
RICHARD HABER, MD: The synthetic versions of thyroxine, which are certainly the more common way the hormone is given now, are purer because they're synthesized to be pure. When you extract thyroxine from the natural sources, which are animal thyroid glands, the thyroxine comes in a mixture with other forms of thyroid hormone that naturally exist in the animal's thyroid gland. There are two forms of the hormone that occur in a thyroid gland-- T4, which is thyroxine, and T3. When someone is taking hormone replacement from the natural source, which is the animal, they're getting a mixture of T4 and T3. That's the way it comes. For a variety of reasons we think it's preferable to give the pure T4 that you get from the synthetic preparation.
Can you explain some of those reasons?
MELISSA KATZ, MD: T4, also called levothyroxine, is the most commonly prescribed form of hormone replacement therapy for hypothyroidism. There are some patients that do express an interest in taking the natural source, which includes T3. But we definitely feel that it is healthier to take replacement with the synthetic levothyroxine, which contains only T4. There are side effects associated with T3, including a predisposition to osteoporosis, and the onset of cardiac arrhythmias in some patients.
RICHARD HABER, MD: The body needs T3 and the thyroid gland makes some naturally. But that's not the same as saying you have to give it. The majority of T3 in the body results from the circulation of T4, or thyroxine in the body. In other words, if you give a patient pure T4, their body -- even if they're hypothyroid -- will make their daily supply of T3 just as it normally does. For this reason, you don't need to actually give it to a hypothyroid patient.
You might as well start with the T4 and the body will do the rest.
RICHARD HABER, MD: Right.
When should treatment begin after a hypothyroid diagnosis? Should it begin immediately?
MELISSA KATZ, MD: I definitely think so. If a patient has a TSH level (which is an excellent and very sensitive test that discerns hormone levels in the blood) that's over 10 or just an abnormal TSH level in a category that's often referred to as subclinical hypothyroidismmy preference is to start treatment immediately because hypothyroidism will usually accelerate. Certainly if you are an elderly patient or somebody that may have underlying heart disease, you might want to be very, very cautious, as rapid replacement with too much thyroid hormone may precipitate heart problemsBut I find that most patients are very grateful and do quite well when they're started on thyroxine.
So if a patient has subclinical hypothyroidism and isn't being treated, caution is warranted? RICHARD HABER, MD: Most of us like to treat patients even if their hypothyroidism is subclinical, for several reasons. In addition to being symptomatic, there are additional risks of being slightly low in thyroid hormone, such as high cholesterol, and a risk of cardiac diseaseand the disease tends to progress, though very slowly over many years. By getting a patient on thyroid hormone replacement early, maybe before it's absolutely necessary, you preempt them from flipping into a really symptomatic hypothyroid state where they really don't feel good, which can happen quite insidiously.
MELISSA KATZ, MD: Women who are pregnant or considering being pregnant, and have suboptimal levels of thyroid hormone, should be started on treatment early to ensure normal growth and development of their babies in the womb.
What are some of the side effects of levothyroxine?
MELISSA KATZ, MD: If you're taking too much, you may have symptoms of hyperthyroidism, such as palpitations. You may have anxiety, sensation of warmth or perspiration. That would be from an inappropriate dose.
The thyroid is a small butterfly-shaped gland that wraps around the windpipe in the front of the neck, and plays a critical role in the body's metabolism. Metabolic disorders occur when the thyroid secretes too little or too much thyroid hormone, and these disorders can affect almost every aspect of health.
Hypothyroidism is a very common condition among women in which the amount of thyroid hormone in the body drops below normal levels. One treatment strategy involves replenishing the body with a synthetic hormone called levothyroxine. How effective is it? And how do the various formulations differ? Below, two experts in the treatment of thyroid disorders discuss medications for this common condition.
How do you treat hypothyroidism?
MELISSA KATZ, MD: Women are the most commonly affected by this condition, and most of them respond very well to treatment with levothyroxine.
What is levothyroxine?
RICHARD HABER, MD: Levothyroxine, or thyroxine, is the naturally occurring hormone that the thyroid gland secretes. It's the principle form of thyroid hormone secreted by the thyroid gland. For those people who don't make thyroid hormone naturally, the drug form of levothyroxine can be used as a replacement. You can get levothyroxine from natural sources, which is comprised of animal thyroid gland that's been ground up and dried. That's the oldest way to do it and this method goes back to the 19th century. The same molecule can be synthesized by chemists. The synthetic drug is currently the way the best selling preparations are made. But the molecule thyroxine, whether synthesized in a chemistry laboratory or extracted from animal thyroid glands, is the same.
A lot of people, when they hear the word "synthetic", immediately think that somehow it's not as effective or it carries some harm and that natural is better. But the point you're making is that a molecule is a molecule.
RICHARD HABER, MD: Right.
How would you compare the purity of hormone in natural vs. synthetic products?
RICHARD HABER, MD: The synthetic versions of thyroxine, which are certainly the more common way the hormone is given now, are purer because they're synthesized to be pure. When you extract thyroxine from the natural sources, which are animal thyroid glands, the thyroxine comes in a mixture with other forms of thyroid hormone that naturally exist in the animal's thyroid gland. There are two forms of the hormone that occur in a thyroid gland-- T4, which is thyroxine, and T3. When someone is taking hormone replacement from the natural source, which is the animal, they're getting a mixture of T4 and T3. That's the way it comes. For a variety of reasons we think it's preferable to give the pure T4 that you get from the synthetic preparation.
Can you explain some of those reasons?
MELISSA KATZ, MD: T4, also called levothyroxine, is the most commonly prescribed form of hormone replacement therapy for hypothyroidism. There are some patients that do express an interest in taking the natural source, which includes T3. But we definitely feel that it is healthier to take replacement with the synthetic levothyroxine, which contains only T4. There are side effects associated with T3, including a predisposition to osteoporosis, and the onset of cardiac arrhythmias in some patients.
RICHARD HABER, MD: The body needs T3 and the thyroid gland makes some naturally. But that's not the same as saying you have to give it. The majority of T3 in the body results from the circulation of T4, or thyroxine in the body. In other words, if you give a patient pure T4, their body -- even if they're hypothyroid -- will make their daily supply of T3 just as it normally does. For this reason, you don't need to actually give it to a hypothyroid patient.
You might as well start with the T4 and the body will do the rest.
RICHARD HABER, MD: Right.
When should treatment begin after a hypothyroid diagnosis? Should it begin immediately?
MELISSA KATZ, MD: I definitely think so. If a patient has a TSH level (which is an excellent and very sensitive test that discerns hormone levels in the blood) that's over 10 or just an abnormal TSH level in a category that's often referred to as subclinical hypothyroidismmy preference is to start treatment immediately because hypothyroidism will usually accelerate. Certainly if you are an elderly patient or somebody that may have underlying heart disease, you might want to be very, very cautious, as rapid replacement with too much thyroid hormone may precipitate heart problemsBut I find that most patients are very grateful and do quite well when they're started on thyroxine.
So if a patient has subclinical hypothyroidism and isn't being treated, caution is warranted? RICHARD HABER, MD: Most of us like to treat patients even if their hypothyroidism is subclinical, for several reasons. In addition to being symptomatic, there are additional risks of being slightly low in thyroid hormone, such as high cholesterol, and a risk of cardiac diseaseand the disease tends to progress, though very slowly over many years. By getting a patient on thyroid hormone replacement early, maybe before it's absolutely necessary, you preempt them from flipping into a really symptomatic hypothyroid state where they really don't feel good, which can happen quite insidiously.
MELISSA KATZ, MD: Women who are pregnant or considering being pregnant, and have suboptimal levels of thyroid hormone, should be started on treatment early to ensure normal growth and development of their babies in the womb.
What are some of the side effects of levothyroxine?
MELISSA KATZ, MD: If you're taking too much, you may have symptoms of hyperthyroidism, such as palpitations. You may have anxiety, sensation of warmth or perspiration. That would be from an inappropriate dose.
