Secretion is a stimulus for the synthesis of human chorionic gonadotrophin by first trimester human placenta.

Time course of release of immunoreactive hCG to a placental incubation in the medium revealed a steady increase over a period of 4 hours. However, levels in the tissue, showed an increase at 10' and 60' after an initial decrease. Studies using A23187 which stimulated secretion also revealed a net increase in the quantity of hCG in the tissue. These results suggest that the secretion of hCG acts as a stimulus for fresh synthesis of hCG.