Levothyroxine Linked to Fracture Risk
As we all age, many of us discover that we have underactive thyroid glands that require medication to treat hypothyroidism. The medication used is, levothyroxine, and it's a synthetic form of the hormone our thyroid gland produces. A new study showed, that levothyroxine, taken in excess, can lead to bone fractures.
According to Geriatrician and researcher Paula A. Rochon, MD, MPH, of Toronto's Women's College Research Institute, says thyroid hormone levels naturally decline with age, but dosages of hormone-replacement therapy often do not reflect this.
As a result, treated patients may end up with an excess of thyroid hormone, or hyperthyroidism, which has been linked to bone weakening. 
It is not unusual for our thyroid needs to change as we age, and medication adjustments must reflect these changes.
For those of you with this disorder, you are probably used to having your thyroid levels checked often to see if an adjustment needs to be made, depending on how much you are producing at any given time. When patients receive an excess of thyroid medication they are at greater risk for fractures, falls, arrhythmias, a loss of muscle strength and neuromuscular function.
In a study done at the University of Toronto, Toronto Canada, researchers studied 213,511 men and women, seventy years of age or older, who received levothyroxine between April 1, 2002 and March 31, 2007. An additional observational study continued to March 31, 2008 to watch for fractures of the wrist, forearm, spine, lumbar spine, pelvis, ankle, lower leg and hip or femur. During this follow-up period, hospital records were used to determine the number of fractures in this cohort group who were given varying doses; these doses were described as current use, past, recent or remote. High dosing of levothyroxine was >0.093 milligrams per day, medium dose was 0.044 - 0.093 milligrams per day and the lowest dose was <0.044 milligrams in the time frame proceeding the fractures. Of these cohort members (22,236), 10.4 % had at least one fracture and (88%) occurred in women involved in the study. 
The greatest risks were in the group who took the highest current dose, which translated into a 3.5 fold greater risk of fracture, compared to those on the lowest dose.
When other risk factors for fractures were included in the study, levothyroxine users had a greater risk of hip fracture, in both men and women.
If you are currently taking this medication, be sure to re-visit your dosing going forward, to help prevent this type of fracture from occurring.
Does this warning apply to those men and women taking this medication who are under the age of 70? Since the study didn't mention this, we don't know. If you are concerned about this risk with levothyroxine, speak with your health care provider about this issue and possibly dosage regulation.
- Thyroid Drug Linked to Fracture Risk in Older Adults Laurie Barclay MD April 2, 2011 http://www.medscape.com/viewarticle/741887
- Thyroid Drug Linked to Fracture Risk in Elderly WebMD, April 29, 2011 http://www.cbsnews.com/stories/2011/04/29/health/main20058640.shtml