thyroid stimulating hormone (TSH) . It's important to note that while the current normal reference range varies slightly from lab to lab, it's generally in the vicinity of 0.4-4.5mIU/L. However, only just a few years prior, the normal reference range using the exact same equipment and methodology was 0.4-5.5mIU/L. But patients didn't change overnight, euthyroid before falling asleep and then waking up hypothyroid, although that is essentially what we claimed happened when the reference range changed.The point I want to make about the To understand the magnitude of this article, we need to step back and undertake a quick review of thyroid testing. Current laboratories around the country use a third generation method for assessing normal reference range for TSH is that it is statistically based, like all other tests. We take one thousand normal adults and measure their results. We then throw out the highest 25 values & lowest 25 values, leaving us w/950 normal which covers 95% of the population. But in labeling the 25 highest & 25 lowest values abnormal, let's remember that all blood samples were drawn from clinically normal patients. These patients weren't clinically ill but we just labeled them as abnormal.
Now, flip that same scenario around. Let's say that your TSH used to hover around 1-1.5mIU/L when you felt "normal" although you might not have known that unless you checked. Then let's say you develop symptoms of hypothyroidism confirmed by TSH >10mIU/L. In response, we start you on levothyroxine and give you just enough to get your TSH below 4.5mIU/L and then tell you that you're normal. But you still don't feel right, not like you did before you developed hypothyroidism. Just like Oliver Twist asking for more gruel, you plead for more levothyroxine. Unfortunately, most of my colleagues just sneer back and ignore you because "your results are normal."
If the above scenario didn't quite hit home, imagine yourself back in school. You're aiming to be your class valedictorian w/straight A's. But there's a fly in the ointment. You just can't understand some class, let's say statistics. So you fail. Luckily, your teacher is willing to tutor you, but then you find out, s/he will only teach you just enough to pass, but no more. S/he won't spend the energy/effort to help you truly understand the importance of statistics and to help you get an A. After all, a D grade is passing, right? No argument there! But it's just not the same for you, the budding valedictorian.
And so it is w/treatment of hypothyroidism . That's why this clinical review, as extensive as it is, really & truly represents a change in direction, at least for two leaders in the specialty of endocrinology. Luckily for you & me, many of my other colleagues are ahead of the ball and treating their patients to clinical goals rather than just numerical ones. These same colleagues have also been willing to consider the addition of triiodothyronine if necessary, as suggested in the text. So if you have hypothyroidism and you just don't feel like yourself on your current regimen, show your family physician or endocrinologist this clinical review. And do your best Oliver Twist imitation.