[On the circadian changes of concentration of free amino acids in pregnancy (author's transl)].

Concentrations of 17 free amino acids were measured in the serum of 15 healthy pregnant women at the end of pregnancy in intervals of 4--5 h. A circadian rhythm with its concentration peak at 5 p.m. could be observed for Ser, Val, Met, Ile, Leu, His, Lys and Arg. Exogenic and endogenic synchronizators are being discussed as possible causes for these fluctuations during the day. The rhythm of the free amino acids makes it necessary that only fasting blood is examined and that the time of day is always registered when the blood specimen is taken.