['To investigate melatonin production in hyperandrogenic women before and during treatment with cyproterone acetate and ethinyl estradiol (Diane 35).', 'We studied 10 women with late onset adrenal hyperplasia due to 21-hydroxylase deficiency (LOCAH) and 10 women with idiopathic hirsutism (IH). Patients were treated with Diane 35 for four months. Fasting blood samples for the determination of luteinizing hormone (LH), follicle-stimulating hormone (FSH), testosterone and dihydroepiandrosterone sulfate (DHEAS) and 24-hour urine collections for the determination of 6-sulfatoxymelatonin (aMT6s) excretion were obtained from all patients at baseline and after 4 months of treatment. Results were compared with those obtained in 15 control women.', 'At baseline, women with LOCAH had significantly higher serum testosterone, 17-hydroxyprogesterone (17OHP) and ACTH stimulated 17OHP values than IH and control women. Their aMT6s values (51.0+/-20.5 mg/24h) were significantly higher than the values in IH (34.3+/-7.1) and control women (30.5+/-6.5) (p< 0.001). Diane 35 treatment significantly decreased serum LH, FSH and testosterone levels and aMT6s values in LOCAH patients (29.8+/-16.6 mg/24h) (p<0.0001) in LOCAH patients.'] Does cyproterone acetate-ethinyl estradiol treatment alter urinary 6-sulfatoxymelatonin excretion in hyperandrogenic women?