[Neopterin variations during the menstrual cycle]

During a complete estrous cycle Neopterin levels were followed up daily in sera of six healthy female volunteers below 30 years of age. Average values found in these individuals were within the normal range. Only two single data--measured on the 29th and the 30th day of one test person's estrous cycle--out of 145 were elevated (between 10 and 15 nmol/l). Therefore elevated Neopterin values of clinically healthy persons should only be taken as an indicator for pathological activation of the cellular immune system if the elevation continues after repeated confirmation in a possibly different estrous phase.