Figure 4.

Evolution of maternal plasma levels of GH (N and V) and IGF-I during pregnancy. As pregnancy progresses, placental GH-V increases in the maternal blood. This leads to increased IGF-I levels and decreased GH-N levels. The decrease of plasma GH-N is due to the negative feedback that GH-V and IGF-I directly exert on pituitary GH-N secretion and also due to the fact that both GH-V and IGF-I stimulate hypothalamic somatostatin secretion that, in turn, negatively controls pituitary GH-N release. The maternal increase in plasma levels of IGF-II is not shown in the figure. Red arrows indicate negative control.