Low-dose GnRH agonist therapy for the management of endometriosis

In order to examine whether treatment with a GnRH agonist alone can maintain estrogen levels within the "estrogen window" that inhibits endometriosis without influencing bone-mineral density, we studied the effects of GnRH agonist therapy and changes in bone-mineral density.

Buserelin acetate nasal spray was administered 3 times a day for 8 weeks (daily dose, 900 micrograms) to 21 women with endometriosis. The drug was then given twice a day for 16 weeks (daily dose, 600 micrograms). The total duration of treatment was 24 weeks. The bone-mineral density of the lumbar vertebrae was measured by dual-energy X-ray absorptiometry before treatment (baseline), at the end of treatment, and 24 weeks after the end of treatment.

The bone-mineral density of the lumbar vertebrae at the end of treatment was 2.44% +/- 0.46% (mean +/- standard error) lower than the baseline value. The value at 24 weeks after the end of treatment was 1.10% +/- 0.64% lower than the baseline value. More than 80% of the patients had serum-estradiol levels of 45 pg/ml or less. During treatment, more than 90% of the patients had serum-estradiol levels of 60 pg/ml or less. Genital bleeding was inhibited in 90% of the patients. After 8 weeks of treatment, the clinical symptoms improved in 75% of the patients; such improvement persisted for the duration of the treatment.

Decreasing the dose of GnRH agonist during treatment can minimize the loss of bone-mineral density without lessening the beneficial effects on endometriosis. This technique might be useful in the management of endometriosis.