Navigating Thyroid Disease

Most people with hypothyroidism take a generic Synthroid tablet to treat it and feel fine. But this is not true for everybody, and if you fall in that category, this article is for you.

The standard treatment for hypothyroidism is levothyroxine. This is synthetic thyroxine, also known as T4. It is the same as what the human thyroid makes, so it is bioidentical. T4 is the less active form of the hormone. When you make your own T4, or take a prescription levothyroxine, your body will convert some of it into the more active form, triiodothyronine, T3. This happens in the peripheral tissues, not in the thyroid. T4 can also get converted into reverse T3– more on that later.

For most people, it does not matter if they get generic levothyroxine or a brand name like Synthroid. Some people might feel better on one preparation or another, and this can be true even for other brand names and generics made by different manufacturers. If you find one you feel particularly good on, pay attention to the manufacturer name on the Rx label. Some people with low stomach acid because they are on a proton pump inhibitor for heartburn or who have had weight loss surgery may have better absorption with a liquid or gel cap version of T4, instead of the usual tablet. Tirosint-SOL is the brand name of the liquid form.

Levothyroxine is a long-acting medication and just needs to be taken once a day. In fact, because it is long acting, some people can take different doses on different days of the week to average out to the right dose for them. This usually works fine, because the usual half life of levothyroxine is 6-7 days. It is traditionally taken first thing in the morning, before eating. If it is hard to remember that or to not eat for an hour after waking up, it can instead be taken before bedtime because it is long-acting and likely won’t interfere with sleep

For people who feel that their hypothryoid symptoms are not adequately addressed by levothyroxine alone, liothyronine can be added. Liothryonine is synthetic, bioidentical, T3. Taking the brand name, Cytomel, does not clinically make a difference for most people. The downside of all T3 medicine is that it is short-acting; its half life is 18 hours. Some people do fine with taking it once in the morning with their levothyroxine but most people need to take it twice a day, to avoid an afternoon dip or crash. I also see that many of my patients find it challenging to consistently take something mid-day with their busy lives. Another down side of the standard T3 medication is that it only comes in three strengths–5, 25, and 50 mcg–so people often have to cut the tablets to get the right dose. (50 mcg is a very high dose because T3 is 3-4 times more potent than T4, and it is rarely used.). Getting T3 from a compounding pharmacy you trust can help with both of liothyronine’s problems; it can be made in any dose and it can be compounded into a slow release formula that is just taken once a day. A compounding pharmacist can also combine t4 and slow release t3 all in one capsule.

Dessicated thyroid is sometimes called the “natural” thyroid medication because it is made from pig thyroid extract. This was the original thyroid medication available for hypothyroidism, and Armour is the best known brand. Most physicians prefer that their patients take the synthetics because the dosing is more specific–the tablet amounts are in micrograms for the synthetics compared to milligrams for desiccated thyroid. But some of my patients feel better on Armour, and this has also been demonstrated in some studies. All the desiccated thyroid medications are a combination of T4 and T3. I think of choosing between synthetic and desiccated thyroid medications as like someone treating a vitamin C deficiency: the synthetics are like taking a vitamin C tablet and desiccated thyroid is more like eating part of an orange. With the desiccated thyroid, you are getting other things in there beside t3 and t4 and they may or may not feel good for you. My patients on stable dosing of desiccated thyroid maintain stable hormone levels. I think the idea that it causes swings in thyroid hormone levels is a myth.

Regardless of what type or combination of thyroid medicine you take, you need to measure labs routinely and after making a change. Taking a synthetic T3 or desiccated thyroid with T3 in it does not mean that it is okay to have a suppressed TSH. Six weeks is the right amount of time to check labs after switching thyroid medicines or changing a dose. I prefer that my patients hold on taking their thyroid medicine pills until after they have their blood drawn. That way I know I am seeing T3 at the lowest point and not spiked from ingesting it an hour or two before. I order TSH, free T3, free T4 and reverse T3. Reverse T3 is made from T4, like regular T3. It is an inactive form but it can bind to the same receptor sites as T3. I find it helps to guide the medication balance when someone is taking both T3 and T4.