Spironolactone but not flutamide administration prevents bone loss in hyperandrogenic women treated with gonadotropin-releasing hormone agonist

GnRH agonists (GnRHa) have recently been proposed for the treatment of hirsutism in women with the polycystic ovary syndrome (PCOS). As most of these subjects have increased androgen secretion from both ovaries and adrenal glands, the association of GnRHa with antiandrogen drugs might enhance the clinical response to treatment. On the other hand, this association might also potentiate the adverse effects of GnRHa on bone metabolism, generating a potentially harmful situation at the skeletal level. In this study we investigated in 41 PCOS patients the skeletal effects of a 6-month course of GnRHa (tryptorelin, 3.75 mg, i.m., monthly), either alone (n = 12) or associated with the antiandrogen drugs spironolactone (100 mg, orally, once daily; n = 14) or flutamide (250 mg, once daily; n = 15). In all subjects bone mineral density was measured before and after treatment by dual energy x-ray absorptiometry at the lumbar spine (L2-L4) and at the femoral neck and Ward's triangle. In addition, at baseline and after 6 months of therapy, bone metabolism markers (serum and urinary calcium, serum phosphorus and alkaline phosphatase, plasma osteocalcin, and urinary hydroxyproline) and endocrine parameters (serum gonadotropins, estradiol, and free testosterone) were assayed. Women given either GnRHa alone or associated with spironolactone or flutamide were similar for age and body mass index. At baseline, the 3 groups of PCOS women were also similar for endocrine and bone parameters. After 6 months, all treatments determined similar striking suppressions of serum gonadotropins and sex steroids. Concurrently, bone mineral density was significantly reduced at all examined sites in subjects receiving either GnRHa alone or GnRHa plus flutamide. Conversely, women given GnRHa plus spironolactone did not show any change in skeletal mass from baseline values (P < 0.05-0.01 among groups). Biochemical parameters of bone metabolism were consistent with densitometric assessments. In conclusion, after a 6-month course of therapy, bone mineral density is reduced in PCOS women given either GnRHa alone or GnRHa plus flutamide, but not in those receiving GnRHa plus spironolactone. The mechanisms of the bone-sparing effect of spironolactone remain to be determined. Nevertheless, this drug could represent a useful tool to prevent skeletal loss in women given GnRHa as well as in other hypoestrogenic conditions, in particular when estrogens are not recommended.