Placenta: which effect regarding insulin?

• A. Insulin antagonist
• B. Insulin mimetic
• C. Insulin secretagogue
• D. Insulin resistance enhancer

Answer: (A)

Placental hormones reduce how responsive maternal tissues are to insulin, shifting glucose toward the fetus. This action opposes insulin’s effects, so the placenta functions as an insulin antagonist. Hormones like human placental lactogen, along with other pregnancy-related hormones, elevate maternal blood glucose by dampening glucose uptake in tissues such as muscle and fat. They do not mimic insulin or stimulate its secretion; instead they blunt insulin signaling, increasing insulin resistance. Clinically, this mild insulin resistance is normal in pregnancy, and if the pancreatic beta cells can’t compensate, gestational diabetes can develop.