Melatonin, placental growth factor and placental hormones at placental insufficiency

Abstract

A pineal gland attracts much attention of scientists lately, because it secrets melatonin, which is a very important hormone. Melatonin plays a significant role in the development of pregnancy: it enhances implantation, decreases oxidative stress etc. At the same time, the links between the pineal gland and the placenta, as a part of endocrine system of a mother, are still not well described. Objective of the study. To investigate the pathogenic links between secretion of melatonin, placental growth factor and reproductive hormones in pregnant women with placental insufficiency, manifested as intrauterine growth restriction syndrome of fetus. Material and methods. 35 pregnant women aged 18-36 with placental insufficiency (PI) were examined (study group). The placental insufficiency manifested as the intrauterine growth restriction syndrome of the fetus (IUGR) in the 3rd pregnancy trimester. The control group consisted of 20 women with uncomplicated pregnancy at the same term. The blood concentrations of melatonin and placental growth factor (PlGF) were studied, as well as the blood concentrations of certain placental hormones: progesterone, placental lactogen and unconjugated estriol. Results. The concentration of melatonin was found to decrease significantly, if pregnancy was complicated by intrauterine fetal growth retardation (study group – 129.90 ± 17.65 pg/ml, control group – 231.25 ± 21.56 pg/ml, p < 0.01), as well as concentration of PlGF (study group – 130,78 ± 15,80 pg/ml, control group – 230.0 ± 29.97 pg/ml, p < 0.01). A significant difference of progesterone concentrations between the groups was found (study group: 15.36 ± 2.78 ng/ml, control group: 30.43 ± 2.66 ng/ml, p < 0.01), as well as for placental lactogen (study group: 6.31 ± 2.08 mg/l, control group: 7.76 ± 1.93 mg/l, p < 0.05). No significant difference between the concentrations of unconjugated estriol was found. A close correlation between melatonin and progesterone in the control group was found (r = 0.76, P = 0.0001), a moderate correlation between melatonin and unconjugated estriol was also established in the control group (r = 0.61, P = 0.004), and a moderate negative correlation between melatonin and placental lactogen was found in the study group (r = -0.438, P = 0.042). Conclusions. The blood levels of melatonin and PlGF significantly decrease in case of placental insufficiency, manifested as intrauterine fetal growth restriction syndrome. In healthy pregnant women, the secretion of steroid hormones (progesterone and unconjugated estriol) by placenta directly correlates with blood concentration of melatonin. This link is being disordered in case of placental insufficiency.