OBJECTIVE The present study investigated the pharmacokinetics of a single subcutaneous dose of human menopausal gonadotropin (hMG) on serum follicle-stimulating hormone (FSH) and luteinizing hormone (LH) concentrations. METHODS Six healthy female volunteers, aged 20-40 years, with regular menstrual cycles and normal endocrine profiles, who were not receiving any hormonal medication, were treated with the gonadotropin-releasing-hormone agonist buserelin to suppress endogenous gonadotropin release. One volunteer dropped out during treatment. When the serum estradiol concentration had fallen to below 500 pmol/L, an injection of 150 IU hMG (HumegonR) was given subcutaneously. Immediately before injection and 0.5, 1, 2, 3, 4, 6, 8, 10, 12, 15, 20, 24, 48 and 96 hours after, blood samples were drawn for determination of FSH and LH concentrations. RESULTS The baseline FSH level was 2.8 IU/L, and peak concentration (6.8 IU/L) was reached 12 hours after hMG injection (median values). Exogenous LH could not be measured because of the presence of endogenous LH. CONCLUSIONS The pattern of serum FSH concentrations after a single injection of hMG was found to resemble that seen after intramuscular hMG administration, although the peak FSH value was reached somewhat later.