Remember my Goldilocks theory of medicine? You want just the right amount, not too much and not too little. In a nested case-cohort study published last week in BMJ, the authors concluded that levothyroxine dose is associated w/osteoporotic fracture in the elderly after following 213,511 patients >70 years old who were either currently taking, or had remotely taken, levothyroxine. They noted that those on high (>93mcg/d) and medium dose (>44mcg/d but <93mcg/d) had more than 2-3x risk of fracture compared to those taking low dose (<44mcg/d) of levothyroxine.
One downside to the study, which the authors acknowledged up front, was their inability to ascertain the patients' TSH. In other words, dose alone is not the final parameter for treatment of hypothyroidism but rather TSH within the normal range (again neither too high nor too low). Admittedly, the higher one's levothyroxine dose the greater one's risk for iatrogenic hyperthyroidism.
The take home point is not to stop taking levothyroxine but rather to continue to monitor one's TSH even after years of taking the same dose, especially since one's physiologic requirement for levothyroxine decreases with age. By the way, don't forget to take your levothyroxine on an empty stomach at night! And don't forget your calcium & vitamin D, too, to maximize bone strength - just remember to take these at a different time than your levothyroxine!
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