Plasma human placental lactogen profiles over 24 hours in normal and diabetic pregnancy.

Plasma human placental lactogen (HPL) concentrations have been measured at frequent intervals over 24 hours in 24 normal women, 13 chemical and 13 insulin dependent diabetic patients during the third trimester of pregnancy. Most of the women studied displayed variation in HPL levels during the day, but there was no evidence of a diurnal rhythm, nor significant changes following meals or during the nocturnal fast. The mean plasma HPL concentrations over 24 hours in the chemical and insulin dependent diabetic patients (5-9+/-SD 1-3 and 5-9+/-1-7 microng/ml respectively) were greater than those in normal women (5-1+/-1-2 microng/ml) but this difference was not significant. No significant change in plasma HPL concentrations was observed during a five-hour oral glucose tolerance test in either the normal or chemical diabetic group. It is suggested that in normal pregnant women HPL does not itself contribute to glucose homeostasis but acts as a 'regulator' which alters the actions of certain maternal hormones to achieve a favourable environment for fetal growth.