Bone Loss

"I'm a 54 year old female and have been taking Synthroid five years to shrink a goiter. My doctor now wants me to Fosamax as a preventive against bone loss. I cannot take HRT, also show now signs of bone loss from the scans. Will Fosamax be given to thyroid patients as a routine preventive?" -- JP, Naples, FL

If you are hypothyroid, and taking replacement doses of levothyroxine to restore TSH to normal, there is no adverse effect on bone density. If you are taking slightly higher doses of levothyroxine that result in suppression of TSH in order to shrink goiters or nodules, or to prevent growth of thyroid remnants after surgery for benign of malignant goitrious tissue, then there may be a risk of reduced bone density.

While controversial, bone loss with suppressive doses of thyroid hormone appears to be a problem for postmenopausal women who are not taking estrogen supplements. Estrogens appear to prevent the loss in bone density. Preliminary studies have shown that biophosphonates can also be used to prevent thyroid hormone related bone loss. Fosamax is the newest biophosphonate to become available, and I know of no studies that have examined the effects of this particular agent on thyroid hormone mediated bone loss. However, one would anticipate that it would be at least as effective as the older biophosphonates that have been studied.

Interestingly, animal studies suggest that calcitonin therapy does not prevent thyroid hormone mediated bone loss. In addition to estrogen, or Fosamax, it is essential to take adequate calcium and vitamin D; for example, 1000 mg of elemental calcium and a multivitamin pill.