Drug Options
People who have hypothyroidism need thyroid hormone replacement, and they'll probably need it for the rest of their lives. Once the right dosage is established, thyroid hormone replacement works well and is safe and easily tolerated. You'll soon notice that your symptoms will ease up and your health will improve. Blood tests will reveal that your T4 and TSH levels are back to normal.
But sometimes, establishing the right dosage of thyroid hormone replacement can be tricky. It may take a few months before you and your doctor figure out the right amount. After all, what works for one patient with a similar profile may not always work for another. Working with your doctor, you will have to experiment with different dosages and get regular blood tests before you pin down the one that works for you.
You also need to make sure you are on the correct form of thyroid hormone replacement. These drugs come in different varieties and brands. You may fare better on one brand or type than you would on another, and it may take some time and experimenting before you figure out which one works best. In addition, you'll need to take and store these drugs correctly.
Synthetic T4
Most doctors today start their hypothyroid patients on synthetic T4. Although T3 is the active form of thyroid hormone, T4 is readily converted to T3 in body tissues. T4 is also the more stable form of thyroid hormone, which helps ensure that blood levels of thyroid hormone remain more even, so that you don't experience the highs and lows that come with taking T3.
The generic name of synthetic T4 is levothyroxine, which is sold under several brand names, the most popular being Synthroid. Although Synthroid was prescribed for years, it did not receive approval from the U.S. Food and Drug Administration until 2003. Since its debut in the 1950s, it had been considered an equivalent of natural hormone (Armour) and so was grandfathered in and spared the approval process required of new drugs. But concerns about potency and stability prompted the FDA to revisit all levothyroxine products and require their manufacturers to apply for approval as new drugs.
By 2004, Synthroid was the second most popular drug in the United States — behind Lipitor, the cholesterol-lowering agent — with more than 42 million prescriptions sold. Other brand names include Levoxyl, Unithroid, and Levothroid.
Some patients may prefer one brand over another, but all the brands are made of synthetic thyroxine. Like the real T4 that your body makes, synthetic T4 tends to remain in the blood for a long time, providing your body cells with a steady supply of thyroid hormone. If your doctor prescribes one brand for you, you should not switch to another brand without his knowledge. Also, ask your doctor to write “DAW” on your prescription. DAW stands for “dispense as written” and will help ensure that a generic is not substituted. If your pharmacist tries to switch your brand, you should insist on getting the drug you are prescribed.
Levothyroxine comes in different color-coded doses. The 50 mcg pill is white and contains no dye, so that people allergic to dyes have that option. Depending on the dosage you're prescribed, you may take the pills singly or in combination. In some cases, you may be able to cut a pill — they do have a line down the middle for easy cutting — and save some money and trips to the pharmacy.
Essential
Although the active ingredient in all the brands of levothyroxine is the same, different brands contain different fillers and are subject to their own quality controls. That's why it's best to find one brand you like and to stick with it.
For most patients with hypothyroidism, treatment with T4 alone is often successful and adequate. Once on T4, their TSH levels will drop to normal, and symptoms will disappear. But if symptoms don't fade, you may need to be treated with T3 as well.
Synthetic T3
As you probably recall, T3 is the active form of thyroid hormone. The synthetic form of T3 is used primarily to lessen the symptoms of hypothyroidism when preparing for whole-body scans, which require that you become hypothyroid. Synthetic T3 is called liothyronine and is sold under the brand name Cytomel.
Synthetic T3 works in the body for only a few hours, so you need to take several doses a day to derive its benefits. Taking T3 also disrupts the way your body naturally controls and regulates TSH levels. And if you take only T3, you will experience low T4 levels. In addition, taking too much T3 can stress the heart.
Still, some patients with hypothyroidism may require T3 if they continue to have symptoms of hypothyroidism even after their TSH levels normalize from the use of T4. Some experts contend that the presence of symptoms suggests that you are having trouble converting T4 into T3. Others dispute that notion and argue that the problem is really another health issue unrelated to the thyroid.
In any case, some doctors may prescribe T3 to address the lingering symptoms. The science on the use of T3 is mixed: Some studies have suggested that patients do better when they take both T4 and T3. But other studies have found no difference in patients receiving T4 alone versus a combination of T3 and T4.
It's possible, but not proven, that patients with low blood levels of free T3 may benefit from T3 treatment. It is also possible that patients who do not fare well on T4 alone may have low levels of T3 in the brain, which cannot be detected without a brain biopsy.
Alert
It's dangerous to take Cytomel — or any other thyroid hormone for that matter — as a way to lose weight. Too much thyroid hormone certainly can rev up the metabolism and result in weight loss. But many people without a thyroid disorder who take thyroid hormone gain weight because their appetite increases. Taking thyroid hormone can also put you into a state of hyperthyroidism, which can cause heart problems and osteoporosis.
In his practice, Dr. Friedman tends to start patients on T4 by itself and adjust the dosage until their TSH is between 0.5 and 2 mIU/dL. If the patient still has symptoms — despite normal TSH levels — Dr. Friedman might add low doses of T3. (Although Cytomel is taken two or three times a day, patients can use a compounding pharmacy that will make a slow-release T3 that is taken once a day. Unfortunately, most insurance companies will not cover the cost of compounded medications.) Dr. Friedman is more inclined to treat patients with T3 if initial tests showed they had low levels of free T3 in their blood.
If they are given both T4 and T3, he checks to make sure their blood levels of free T4 and free T3 are in the higher end of normal. When patients are on this type of combination treatment, they are likely to have lower levels of TSH since T3 suppresses the TSH.
Synthetic T4 and T3
Some patients who need T3 may be given a drug that combines both T4 and T3. This combination drug is called liotrix and sold under the brand name Thyrolar. The ratio of T3 to T4 in Thyrolar is 1 to 4. If you are prescribed Thyrolar, make sure to store it in the refrigerator.
The disadvantage of Thyrolar is that the T3 to T4 ratio is fixed. If your doctor gives you T3 and T4 separately, she can adjust that ratio to better match your needs.
Desiccated Thyroid Drugs
In the years before synthetic T4 was available, people who had hypothyroidism relied on desiccated thyroid hormone replacement to restore their missing hormones. In fact, Armour, the most well-known brand, was the only thyroid hormone drug on the market for the first half of the twentieth century. Today, it remains a popular treatment despite the use of synthetic thyroid hormone, with almost $2.5 million in sales in 2004, according to
These treatments are made from hormones extracted from the thyroid glands of pigs. They contain both T4 and T3 and are sold under several brand names, Armour being the most popular. Other brands include Bio-Throid, Westhroid, and Nature-Throid. These medications are particularly appealing to patients who prefer using “natural” products to synthetic ones.
Although it has not been proven, some experts believe that desiccated thyroid hormone contains other hormones or factors made by the thyroid, which are not found in synthetic hormones.
Some conventional doctors are more resistant to using desiccated thyroid hormone in their patients, believing that synthetic products are best. But in reality, some patients do better on these products than they do on the synthetic ones. If you are on synthetic hormones and have a normal TSH (0.5–2.0 mIU/dL) but are still not feeling well, you should discuss the possibility of trying natural hormone therapy.
Some people are concerned about the consistency of the different batches of these products. Since the thyroid hormones come from pigs, it is quite possible that the amount of thyroid hormone in the gland of each animal will vary somewhat. On the other hand, most manufacturers do take steps to ensure consistency. Forest Pharmaceuticals, Inc., which makes Armour, for one, says it tests both the powder and the finished tablet to ensure that the amount of hormone is consistent. Any inconsistency that might occur is usually so slight as to be insignificant.
Essential
If you have trouble convincing your doctor that you should try natural hormone therapy, consider finding a more open-minded physician who will let you give it a try. Armour is also much cheaper than synthetic thyroid hormone.
With patients who do not improve on T4 treatment alone or combined T4 and T3 therapy, Dr. Friedman will sometimes switch to a natural treatment, usually Armour, plus synthetic T4. He adds T4 to the regimen to make up for the higher T3 to T4 ratio found inArmour. When he tests them, he looks for free T4 and free T3 in the upper ranges of normal.
