This page and its contentsare Copyright 2005the American Thyroid Association
ADDITIONAL PATIENT RESOURCES
Thyroid hormone is used in two situations: 1) to replace the WWW.THYROID.ORG
function of the thyroid gland, which is no longer functioning For further details on this and other thyroid-related topics,
normally (“replacement therapy
”) and 2) to prevent further
please visit the patient resources section on the AmericanThyroid Association website at
growth of thyroid tissue (“suppression therapy
DEFINITION, THERAPY & TREATMENT
Thyroid hormone replacement therapy
How do I take thyroid hormone?
Many people have a thyroid gland that cannot make enough thyroid
Thyroid hormone is easy to take. Because it stays in your system for a long
hormone for the body’s needs. This is called Hypothyroidism
and may be
time, it can be taken just once a day, and this results in very stable levels
caused by a non-functioning thyroid gland (for example Hashimoto’s
of thyroid hormone in the blood stream. When thyroid hormone is used
disease), by destruction of thyroid gland by surgery or radiation treatment
to treat hypothyroidism, the goal of treatment is to keep thyroid function
or by a non-functioning pituitary gland (see).
within the same range as people without thyroid problems. Keeping the
Hypothyroidism, is the most common reason for needing thyroid hormone
TSH level in the normal range does this. The best time to take thyroid
hormone is probably first thing in the morning on an empty stomach. Thisis because food in the stomach can affect the absorption of thyroid
The goal of thyroid hormone treatment is to closely replicate normal
hormone. However, the most important thing is to be consistent, and take
thyroid functioning. Pure, synthetic thyroxine (T4) works in the same way
your thyroid hormone at the same time, and in the same way, every day. If
as a patient’s own thyroid hormone would. Thyroid hormone is necessary
you are taking several other medications, you should discuss the timing of
for the health of all the cells in the body. Therefore, taking thyroid hormone
your thyroid hormone dose with your physician. Sometimes taking your
is different from taking other medications, because its job is to replace a
thyroid hormone at night can make it simpler to prevent your thyroid
hormone that is missing. The only safety concerns about taking thyroid
hormone from interacting with food or other medications.
hormone is taking too much or too little. Your thyroid function will bemonitored by your physician to make sure this does not happen.
Do not stop your thyroid hormone without discussing this with yourphysician. Most thyroid problems are permanent, and therefore most
How is the dose of thyroid hormone chosen?
patients require thyroid hormone for life. If you miss a dose of thyroid
When someone is first started on thyroid hormone the initial dose is
hormone, it is usually best to take the missed dose as soon as you
carefully selected based on information such as a person’s weight, age,
remember. It is also safe to take two pills the next day; one in the morning
and other medical conditions. The dose will then need to be adjusted by
and one in the evening. It is very important that your thyroid hormone
a physician to keep the thyroid function normal. The physician will make
and TSH levels are checked periodically, even if you are feeling fine, so
sure the thyroid hormone dose is correct by performing a physical
that your dose of thyroid hormone can be adjusted if needed.
examination and checking TSH levels.
Does thyroid hormone interact with any other medications?
There are several brand names of thyroid hormone available. Although
Taking other medications can sometimes cause people to need a higher
these all contain the same synthetic T4, there are different inert ingredients
or lower dose of thyroid hormone. Medications that can potentially cause
in each of the brand names. In general, it is best for you to stay on the
people to need a different dose of thyroid hormone include birth control
same brand name. If a change in brand name is unavoidable, you should
pills, estrogen, testosterone, some anti-seizure medications (for example
be sure your physician is aware of the change, so that your thyroid function
Dilantin and Tegretol), and some medications for depression. Yet other
can be re-checked. If your pharmacy plan changes your thyroid hormone
products can prevent the absorption of the full dose of thyroid hormone.
to a generic preparation, it is important for you to inform your physician.
These include iron, calcium, soy, and some cholesterol-loweringmedications. For all these reasons, it is important for people taking thyroid
A LISTING OF THE FDA-APPROVED MEDICINES
hormone to keep their physician up to date with any changes in the
medications or supplements they are taking.
Unithroid® . AB . (Stevens)*+
L-Thyroxin . AB . (Mylan) *#
Should I take thyroid hormone while I am pregnant?
Levo-T® . BX . (Alara)
Since thyroid hormone is a hormone normally present in the body, it is
Levoxyl® . BX . (Jones)*
absolutely safe to take while pregnant. Indeed, it is very important for
Novothyrox® . BX . (GenPharm)
pregnant women, or women who are planning to become pregnant, to
Synthroid® . BX . (Abbott)*
have normal thyroid function to provide the optimum environment for
Levothroid® . BX . (Forest/ Lloyd)*
her baby. Women who are taking thyroid hormone often need an increased
Levolet® . BX . (Vintage)
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
+ = This is BX rated vs the other name brand LT4s
pregnant. You should discuss the timing of thyroid blood tests with your
# = This is AB rated only to Unithroid and is considered the only “generic”.
physician, but often thyroid function is checked every trimester.
This page and its contentsare Copyright 2005
What about “natural” thyroid hormones?
Will thyroid hormone help me if I have hypothyroid symptoms
Desiccated (dried and powdered) animal thyroid (Armour
®), now mainly
but normal thyroid hormone levels?
obtained from pigs, was the most common form of thyroid therapy before
Some people with normal thyroid blood tests have symptoms that are
the individual active thyroid hormones were discovered. People can still
similar to symptoms of hypothyroidism. Several scientific studies have
buy it over the Internet—legally if it’s sold as a food supplement, but
looked at whether T4 therapy would be of benefit to patients with
illegally if it’s sold as a medicine. Since pills made from animal thyroid
symptoms that overlap with hypothyroid symptoms and normal thyroid
are not purified, they contain hormones and proteins that never exist in
function. In all cases, there was no difference between T4 and a placebo
the body outside of the thyroid gland. While desiccated thyroid contains
(sugar pill) in improving symptoms or well-being.
both T4 and T3, the balance of T4 and T3 in animals is not the same as inhumans, so the hormones in animal thyroid pills aren’t necessarily “natural”
Why would I need thyroid hormone suppression therapy?
for the human body. Further, the amounts of both T4 and T3 can vary in
When thyroid hormone is used to treat hypothyroidism, the goal of
every batch of desiccated thyroid, making it harder to keep blood levels
treatment is to keep thyroid function within the normal range. Thyroid
right. Finally, even desiccated thyroid pills have chemicals (binders) in
hormone can also be used to keep the TSH level in the low, or low normal,
them to hold the pill together, so they are not completely “natural”.
range. This has the effect of turning off one of the signals for thyroid tissue
Desiccated animal thyroid is rarely prescribed today, and there is no
to grow and is known as thyroid hormone suppression therapy. This
evidence that desiccated thyroid has any advantage over synthetic T4.
approach to using thyroid hormone can be used to try and stop thyroidnodules or enlarged thyroid glands from growing. This kind of treatment
What about T3?
needs to be carefully considered before it is tried. It should also be closely
While most actions of thyroid hormone are most likely due to T3, most T3
monitored because of risks of irregular and fast heart rhythms,
in the body comes from the conversion of T4. The conversion of T4 to T3
exacerbation of chest pain and decreased bone density.
is normal in hypothyroid patients. T3 has a very short life span in the body,while the life span of T4 is much longer, ensuring a steady supply of T3. A
Treatment of thyroid cancer
preparation of synthetic T3 (Cytomel
®) is available. After taking a tablet
After surgery for thyroid cancer, thyroid hormone is needed both to replace
of Cytomel® there are very high levels of T3 for a short time, and then the
the function of the removed thyroid gland and to keep any small or
levels fall off very rapidly. This means that T3 has to be taken several times
residual amounts of thyroid cancer cells from growing (see
each day, and even doing this does not smooth out the T3 levels properly.
Thyroid hormone suppression therapy is also an important part
In addition, it is impossible to avoid having too much thyroid hormone in
of the treatment of thyroid cancer and is effective in stopping the growth
the system soon after each dose of T3 is taken. High T3 levels can lead to
of microscopic thyroid cancer cells or residual thyroid cancer. The
unpleasant symptoms such as rapid heart beat, insomnia and anxiety. High
duration of suppression therapy in cancer patients currently being
T3 levels also can harm the heart and the bones. Another concern with
debated. In this case, the benefit of preventing the growth of residual
using T3 treatment is that the body is deprived of the ability to adjust the
thyroid cancer cells outweighs the risks of a mild increase in the risk of
conversion of T4 to T3 to regulate the supply of T3 according to the body’s
fast, irregular heart rhythms, exacerbation of chest pain and decreased
own needs. Thus, there is no indication for the use of T3 alone for the
bone density. A physician should closely monitor this kind of treatment.
What about combined T4 and T3 treatment?
Some hormone preparations containing both T4 and T3 are available in
the United States (Thyrolar®
). Combination T4/T3 preparations contain
much more T3 than is usually produced naturally within the body. Because
ADDITIONAL PATIENT RESOURCES
of this, they can have the same side effects as T3 given by itself. It is also
given once a day, ignoring the short life span of T3 in the body. There has
been interest in whether a combination of T4 and T3, with a lower amount
of T3 given more than once a day, might result in better treatment of
hypothyroidism, especially in those patients that do not feel completely
normal on T4 alone. A trial period of 3 – 6 months is reasonable to
determine if combination T4 and T3 therapy will help.
The following is a list of the most commonly prescribed drugs. It represents an abbreviatedversion of the drug list (formulary) that is at the core of your prescription-drug benefit plan. The list is not all-inclusive and does not guarantee coverage. In addition to using this list,you are encouraged to ask your doctor to prescribe generic drugs whenever appropriate. PLEASE NOTE: Brand-name drugs
INTERVENTIONS COMPRENANT DES SUPPLÉMENTS ALIMENTAIRES OLO ŒUFS LAIT ORANGES Oumar B. Hamza et collaborateurs OUMAR BRAHIM HAMZA : B.Sc, MSc, Dt. p. Nutritionniste consultant Agent de programmation en santé publique, Direction de la santé publique de la Régie régionale de la Montérégie, Conseiller scientifique à l’Institut national de santé publique d