Serum Placental Lactogen Levels During Pregnancy and in Trophoblastic Disease

Abstract

A quantitative radioimmunoassay for human placental lactogen (HPL) in serum is described utilizing a highly purified preparation of HPL. HPL was detected in the serum of pregnant women as early as the sixth week of gestation and the levels rose steadily during the first and second trimesters, reaching a plateau during the third trimester. Serum HPL levels show little variation during the day and are not affected by induced hypoglycemia or hyperglycemia. HPL disappears promptly from the blood after delivery with a half-life in serum of approximately 30 min. Relatively small quantities of HPL were detectable in umbilical cord blood, indicating only a minor transplacental transfer of this protein. HPL was measured in the serum of 6 patients with trophoblastic tumors, and the levels were comparable to those of early pregnancy or lower.