Objectives: The aims of the study were (1) to examine the relationship between leptin and placental hormones by measuring serial changes in serum levels of leptin during and after pregnancy and (2) to study the effects of several gestational hormones on leptin release from fully differentiated 3T3-L1 adipocyte cell cultures.
Study design: Serum levels of leptin were measured throughout pregnancy and at 3 months post partum in 29 healthy women and were also measured in 18 healthy women at delivery by cesarean section and on postpartum day 3. In addition, 3T3-L1 mouse adipocytes were incubated for 24 hours in media containing various reproductive hormones and leptin production was measured.
Results: Serum leptin levels increased significantly (8.4 +/- 0.9 vs 13.5 +/- 1.5 ng/mL; P <.001) between the first 2 trimesters of pregnancy but not between the second and third trimesters. These changes in leptin did not correlate significantly with changes in body mass index. Leptin levels dropped significantly during the immediate postpartum period, from 34.1 +/- 4.9 at cesarean delivery to 7.3 +/- 1.4 ng/mL on postpartum day 3 (P <.001). Fasting insulin level did not correlate significantly with leptin level during pregnancy but did so during the postpartum period (r = 0.60; P <.05). Leptin secretion from 3T3-L1 adipocytes was increased significantly when cells were cultured with human chorionic gonadotropin (150%, P <.01) and also when they were cultured with estrogen (120%, P <.03).
Conclusion: The data suggest that leptin production by adipose tissue is stimulated by several hormones of pregnancy, which may contribute to the increased leptin levels observed during gestation.