Three-Year Follow-up on Effects of Transdermal Estrogen

1 July 1996 | Volume 125 Issue 1 | Page 77

TO THE EDITOR:

In a prospective clinical trial on the treatment of osteoporotic women with hormonal replacement therapy using 100 µg of transdermal estrogen per day plus progestin or placebo, we reported increases of 5.3% in lumbar spine bone mineral density and a significant decrease in vertebral fractures [1]. Hormone replacement therapy was continued for an additional 2 years in 29 of the 39 women in the treatment group, whereas the 39 women in the placebo group crossed over to receive hormone replacement therapy or withdrew from the study.

Lumbar spine bone mineral density continued to increase during follow-up, reaching an asymptote between the second and third year; the overall increase was 12% above baseline (Figure 1). Measurement of biochemical markers (serum osteocalcin, serum bone alkaline phosphatase, and urinary hydroxyproline levels) remained suppressed. Although lumbar spine bone mineral density can increase after antiresorptive therapy, this finding has been attributed to a transient remodeling [2], a process that should last only about 6 months until resorption and formation reach a new steady state. Clearly, some additional process must be invoked to explain these results.

View larger version (8K): [in this window] [in a new window]   Figure 1. Increase in lumbar spine bone mineral density (BMD) during a 3-year follow-up period. TDE equals transdermal estrogen.

 

Increases in lumbar spine bone mineral density have also been reported after bisphosphonate therapy for osteoporosis; this has led some to suggest the existence of a formation-stimulating or bone-building mechanism. Bone mineral density has been reported to increase by 4.2% after 2 years of etidronate therapy [3], by 5.3% after 18 months of pamidronate therapy [4], and by 7.3% after 18 months of alendronate therapy [5]. These increases are no greater than the increase we reported after hormone replacement therapy. Thus, claims of superiority for bisphosphonates over hormone replacement therapy with respect to bone gain should be viewed cautiously until substantial gains in lumbar spine bone mineral density with bisphosphonate therapy have been documented for periods longer than 3 years.

Edward G. Lufkin, MD

B. Lawrence Riggs, MD

Mayo Clinic and Foundation

Rochester, MN 55905

Author and Article Information

Top Author & Article Info References

Mayo Clinic and Foundation, Rochester, MN 55905

References

Top Author & Article Info References

1. Lufkin EG, Wahner HW, O'Fallon WM, Hodgson SF, Kotowica MA, Lane AW, et al. Treatment of postmenopausal osteoporosis with transdermal estrogen. Ann Intern Med. 1992; 117:1-9.

2. Parfitt AM. Morphologic basis of bone mineral measurements: transient and steady state effects of treatment in osteoporosis [Editorial]. Miner Electrolyte Metab. 1980; 4:273-87.

3. Watts NB, Harris ST, Genant HK, Wasnich RD, Miller PD, Jackson RD, et al. Intermittent cyclical etidronate treatment of postmenopausal osteoporosis. N Engl J Med. 1990; 323:73-9.

4. Fromm GA, Vega E, Plantalech L, Galich AM, Mautalen CA. Differential action of pamidronate on trabecular and cortical bone in women with involutional osteoporosis. Osteoporos Int. 1991; 1:129-33.

5. Liberman UA, Weiss SR, Broll J, Minne HW, Quan H, Bell NH, et al. Effect of oral alendronate on bone mineral density and the incidence of fracture in postmenopausal osteoporosis. N Engl J Med. 1995; 333:1437-43.

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