Kurland et al.(1) reported a fascinating case of skeletal fluorosis in a man who probably ingested significant quantities of fluoride from toothpaste. They report that after withdrawal of fluoride, there was a short initial period of rapid bone loss, followed by a prolonged period of slow BMD loss from the lumbar spine—such that the Z-score was still +9 some 8 yr later.
A patient with skeletal fluorosis has attended my clinic for a similar period. At the age of 53 yr, after having sustained two upper limb fractures, she was diagnosed with osteoporosis by a physician and started on calcium supplements, sodium fluoride 40 mg daily, and hormone replacement therapy with ethinylestradiol 20 ug daily (the patient had earlier had a hysterectomy). Ten years later, she was referred to our clinic because a radiograph showed spinal osteosclerosis typical of skeletal fluorosis. The spinal BMD Z-score was +5.8 (T-score, +4.1). The fluoride treatment and calcium supplements were stopped, but she elected to continue her estrogen replacement treatment. We repeated spinal BMD measurements (made on the same Lunar DPX-L densitometer) at intervals over the next 11 yr. Over the next 9 yr, the rate of decline of BMD from the lumbar spine was slow, averaging 0.8% per year, similar to that described by Kurland et al.(1) By the age of 74 yr, she still had a Z-score of +4.9 (T-score, +2.9), and at this point, she stopped taking estrogen replacement. Over the next 2 yr, there was a 10-fold increase in the rate of fall in lumbar spine BMD (~8% per year; Fig. 1). It seems probable that the rate at which skeletal fluorosis can be reversed depends on the underlying rate of bone turnover, and it is substantially slower in subjects who are sex hormone replete and (presumably) in subjects taking antiresorptive drugs.
1. Kurland ES, Schuman RC, Zerwekh JE, Reinus WR, Dempster DW, Whyte MP 2007 Recovery from skeletal fluorosis (an
enigmatic American case). J Bone Miner Res 22:163–170.