Monday, July 26, 2010

Some Musings on Cholesterol and Hypothyroidism

By Diana Hsieh

Dr. Kurt Harris' latest post -- Statins and the Cholesterol Hypothesis, Part I reminded me of some thoughts on cholesterol and hypothyroidism I posted to OEvolve a few months ago. Back in May, I wrote:

On the question of whether high cholesterol is dangerous, I wonder how much the data on that is confused by the fact that hypothyroidism is often undiagnosed or improperly treated.

Hypothyroidism does cause high cholesterol -- and atherosclerosis. It's a major risk factor for heart disease.

Moreover, hypothyroidism is extremely common. It's also under-diagnosed. Many people don't have their thyroid checked regularly. Also, doctors tend to rely exclusively on TSH values, and often permit an outdated wide range for normal. Even once diagnosed, hypothyroidism is most often treated by T4-only medication. That works for some people, but for many others, that's ineffective. That medication leaves all their symptoms intact, while improving only their blood values. So they're put on statins for high cholesterol, anti-depressants for depression, etc.

Undoubtedly, the high cholesterol in undiagnosed or mis-treated hypothyroid people is a warning sign, but that doesn't mean that all high cholesterol is dangerous. However, the fact that so many of those hypothyroid people are running around in the general population might give the false impression that high LDL is a problem per se. I'm doubtful that the epidemiologists are controlling for all that.

However, all that might be secondary to the fact that LDL is calculated rather than measured directly -- and that the single number combines good (i.e. large fluffy) LDL with bad (i.e. small dense) LDL. That's like having a murder rate that includes the birth rate too.

In my own case, my always-high LDL cholesterol improved (as did HDL and triglycerides) after switching to paleo. Then, as I developed serious hypothyroid symptoms, it got worse then ever before. I did a particle size test before I was diagnosed as hypothyroid, and the results weren't great. (That's not too surprising, I think. Later, when I was seriously hypothyroid, I had terrible problems regulating my blood sugar, as if I was subsisting on nothing but pasta and jellybeans, even though I was eating as paleo as ever.) I hope to have another particle size test when my thyroid medication is properly calibrated.
Honestly, I don't know what to think about the relationship between cholesterol and heart disease. From what I can tell, the science seems murky. Maybe in 20 years we'll know.

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