The Tyranny of Blood Levels

So for about 12 years, I've been living with an autoimmune disease.  As autoimmune diseases go, it's the one you want to get: a condition known as Hashimoto's Thyroiditis, which slowly kills off your thyroid.  The diagnosis was a bit of a freak: my primary care physician caught the spike in thyroid hormone which happens at the very start of the disease, tested for the antibodies, and gave me a diagnosis.  For twelve years I've been waiting to find out when, exactly, my thyroid would give up the ghost.


This year, it finally seemed like it had become time.  My hair started to fall out, I got fatigued more easily, my throat developed a permanent growl, and I was cold all the time.  I've never really liked cold--not since I spent a few hours standing on a snowy road in Vermont wearing spandex ski pants and a blazer (don't ask).  But cold started to make me frantic--I would bring multiple sweaters to the movies, and spent most of my time at home wrapped in a slanket.  A light breeze could make me shake.

These are all textbook symptoms of hypothyroidism.  There's only one problem: the numbers didn't show it.

Thyroid deficiency is measured by checking the levels of something called Thyroid Stimulating Hormone (TSH).  When your thyroid levels are too low, your body releases TSH to get things moving again.  Only if your thyroid is conking out, the TSH doesn't do much, so your body releases more.  Most labs consider the "normal" range to be somewhere between 0.5 and 5. 

The American Association of Clinical Endocrinologists now considers this to be too conservative; they've revised their guidelines to between 0.3 and 3.  My TSH levels were right at the edge of the new, narrower range.

There are real risks to taking too much thyroid hormone--it can cause heart palpitations and increase your risk of fractures.  Unfortunately, too little thyroid hormone can leave you fat, bald, constipated, and depressed.

Doctors used to treat mostly based on symptoms; they kept giving you thyroid supplement until you lost weight, regained your hair, and perked the hell up.  If you developed heart palpitations, sweating, insomnia, or anxiety, they cut back your dose.

But then it became easier to test for TSH.  Guidelines were developed--conservative guidelines that erred on the side of hypothyroidism, since being hyperthyroid can kill you, while being hypothyroid just, well, makes you fat, bald, constipated, and depressed.

As a result, as thyroid patients have now been complaining for years, doctors stopped paying attention to the symptoms.  They treated the number instead of the disease.  As long as your levels were under 5, they told you that you were fine and there was nothing more they could do.

Changing the guidelines has helped some, but most primary care doctors just target the numbers they learned in school, and older endocrinologists have also often been resistant to change.  I know several people whose weight gain was clearly entirely due to their thyroid, but whose doctors stopped well short of a dose that would make them lose the weight; when they pointed out that they still had a lot of symptoms (weight gain, but also the baldness and the fatigue and so forth) they were told that they were just drug-seeking for vanity purposes and they should stop eating twinkies and get their fat asses to the gym.

(Okay, I paraphrase.  But that was reportedly the clear implication.)

This is fairly ridiculous--one person I know was living basically entirely on oatmeal and sashimi, and working out so many hours a day that she injured herself rather badly, but the weight didn't come off.  When she finally found a doctor who would get her TSH into a normal range, she lost twenty pounds in 2-3 weeks.  Since presumably endocrinologists are familiar with this phenomenon, I am hard put to understand why they would blithely advise someone to just spend a little more time on the treadmill.

In fact I can understand why doctors want to stick to the number: it is objective, while "I'm tired and kinda blue" is not.  And presumably, you will get idiot patients who want to be thinner than is natural for them, and will lie about their symptoms in order to be prescribed dangerous levels of thyroid hormone.

But this is not much comfort to the thyroid patient struggling to get enough energy to make it through the day.

I think about this a lot when people start talking about "evidence-based medicine" and how it can help us control health care costs.  The question is, "evidence of what?"  Evidence-based medicine works best on things that are very easy to measure, like blood levels.  It is very easy to tell whether a statin reduces blood cholesterol levels.  It took a lot longer to tell whether it actually reduced heart attacks.

The more we rely on a central board to make decisions for huge numbers of people, the more tempted we are going to be to rely on metrics which can be collected, aggregated, and mined for data.  Where does that leave the thyroid patient with "normal" blood levels . . . and a collection of vague, frustrating--but nonetheless very real--symptoms?

As it happens, I found a younger endocrinologist who treats more aggressively--to a level around 1.  Last month, I started on low dose thyroid hormone.  

I am a cynical person who spends a lot of time reading drug studies, so I tend to assume that any effects I experience are from the placebo effect.  In the case of the thyroid hormone, I didn't notice anything at all.  Except that three weeks later I realized I wasn't so cold any more.  And today, it occurred to me that the permanent frog in my throat seems to have hopped away.  

I don't want to come out against evidence-based medicine; we should always be trying to figure out what works and what doesn't, and to reimburse providers accordingly.  

But I do question what constitutes evidence.  Will evidence-based medicine push us even more towards looking at numbers rather than listening to patients?
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Megan McArdle is a columnist at Bloomberg View and a former senior editor at The Atlantic. Her new book is The Up Side of Down.

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