In medicine it is sometimes both funny and sad to watch how drug company marketing and medical politics win out over common sense. An example of this is the argument over which form of thyroid hormone replacement is best.

The answer? Different people do better with different types of thyroid hormone, and you can tell which is best by what feels best to you.

Most doctors use the equivalent of a medication called "Synthroid." This contains only one of the hormones made by your thyroid (T4 or thyroxine, which is not active), and your physician presumes that your body will turn it into the active hormone. This works fine for about two thirds of folks — if the dose is adjusted to how you feel as opposed to being adjusted to only make the blood tests normal.

Basically, it is best for your physician to continue to adjust the dose until you find the level that feels best, and then double check the thyroid blood tests to be sure they are in the normal range for safety.

This is far preferable to simply adjusting the dose until the blood test is "normal," as normal only means that you are not among the highest or lowest 2percent of the population (think of the analogy of a "normal" shoe size, which would only mean somewhere between the sizes 3 and 14).

What can you do if you still feel poorly on the Synthroid (thyroxine)?

When this occurs, many people find they do better by using a form of thyroid that combines both of the major hormones made by your thyroid gland. This is available by prescription (called "Armour Thyroid" — although I prefer the T4 plus T3 combinations made by compounding pharmacies).

Although looking at studies overall suggests that either form has an equal chance of being effective, a recent study suggests that for those who feel lousy on Synthroid (approximately one third), three times as many will prefer the combination T4 plus T3.

This combination can be especially effective in people who also have depression. If your physician is not open-minded enough to consider a trial of this treatment, consider making an appointment with a holistic physician who is trained in this issue.

Can you have low thyroid despite normal blood tests?

Absolutely. In fact, it is conservatively estimated that over 50 percent of people who need thyroid hormone have normal blood tests. So how can you tell?

• Symptoms of low thyroid include fatigue, weight gain, cold intolerance, constipation, infertility, low body temperature and hair thinning. A trial of thyroid hormone may be warranted if you have even one or two of these problems.

• Symptoms of an overactive thyroid feel like having had too much caffeine. These include anxiety, palpitations, shakiness and generally feeling hyper.