PLACENTAL GROWTH-HORMONE LEVELS IN NORMAL-PREGNANCY AND IN PREGNANCIES WITH INTRAUTERINE GROWTH-RETARDATION

To assess the possible role of placental growth hormone (GH) in fetopl acental growth, we measured placental and pituitary GH (GHN) in matern al plasma by means of two RIA using two MAb (5B4 recognizing both plac ental GH and GHN, and K24 recognizing only GHN) during pregnancy. IGF- I also was measured by RIA in the same samples after extraction. A tra nsverse study of 186 samples obtained between 8 wk of amenorrhea (WA) and term confirmed the reported rise in GH immunoreactivity with 5B4 a fter 24 to 25 WA from 12.3 +/- 2.0 mU/L (mean +/- SEM) to a plateau of 27.5 +/- 3.4 mU/L at 34 to 35 WA together with the decrease in GHN to undetectable levels by 24 to 25 WA. IGF-I levels increased from 164.0 +/- 44.6 mug/L at 24 to 25 WA to 331.6 +/- 63.6 gg/L at term. A longi tudinal study of 31 normal pregnant women confirmed this hormonal patt ern and the reported placental GH plateau after 35 WA. A drastic decre ase in placental GH was observed with the onset of labor (from 26.9 +/ - 2.1 to 2.7 +/- 1.1 mU/L), whereas the decrease in IGF-I was not sign ificant (from 212.9 +/- 26.5 to 162.4 +/- 16.9 mug/L). Interestingly, maternal plasma samples obtained after 31 WA until the initiation of l abor in 22 cases of intrauterine growth retardation (six cases of toxe mia, one chromosomal aberration, one maternofetal infection, 14 idiopa thic) contained significantly lower amounts of placental GH (14.9 +/- 1.6 mU/L versus 26.5 +/- 1.2 mU/L in normal pregnancies; p < 0.001). P lasma IGF-I levels were also lower than normal (156.0 +/- 25.5 mug/L v ersus 285.1 +/- 40.8 ug/L; p < 0.001). These results suggest a relatio nship between placental GH levels in the maternal plasma and the devel opment of the fetoplacental unit.