This is an excerpt of a question from Dr Lowe:-
January 25, 2002
I am going to an endocrinologist for the first time in 15 years on Friday to discuss my continuing symptoms of hypothyroid. My question comes here. I had my doctor's office fax my blood test result to me, and I’m very perplexed. The normal range for the TSH my doctor looks at is 0.49-to-4.67. My last two blood tests read less than 0.03. Now, I had my thyroid burned out, so why would my TSH reading be so low, indicating that my thyroid is producing enough hormone. I’m so confused and upset by this and really need some answers. I know I’m going to a specialist in a couple days, but I’d like to go to my appointment armed with as much knowledge as possible. Could it be that my pituitary gland is not functioning properly? I truly appreciate your input.
Dr Lowe: Your observations don’t suggest to me that your pituitary gland isn’t functioning properly. In fact, your observations are consistent with what science tells us about a patient's T4 dose, her TSH level, and her metabolic health or lack of it. If the goal of a doctor is metabolic health for his patient, he has no scientific basis for adjusting her thyroid hormone dose by her TSH level. If the doctor is going to make the imprudent choice of treating the patient with T4 (rather than T3 or a T3/T4 combination), he should be aware of the relevant physiology and treat her on the basis of it. Otherwise, he's likely to ruin her health, as your doctor appears to be doing to yours.
The TSH level is not well synchronized with the tissue metabolic rate. (Probably most doctors falsely assume that studies have shown that the TSH and metabolic rate are synchronized. But despite my diligently searching for years for such studies, I’ve yet to find them.) Adjusting the T4 dose by the TSH level is like adjusting the speed of your car by a speedometer that's out of synchrony with the actual speed of the car. Adjusting the speed of a car by an out-of-sync speedometer, of course, will get the driver into trouble—either with other drivers who'll object to the car traveling too slowly, or with a police officer who'll object to the car going too fast. And adjusting the thyroid hormone dose by the TSH level gets most patients in trouble—almost always because their tissue metabolism is so slow that they are sick.