What effect does human chorionic somatomammotropin have on insulin?

Human chorionic somatomammotropin (hCS), also known as human placental lactogen, plays a crucial role in pregnancy by modulating maternal metabolism to ensure an adequate supply of nutrients to the growing fetus. One of its prominent effects is the induction of insulin resistance in the mother. This effect is essential because it helps to increase maternal blood glucose levels by reducing the effectiveness of insulin. This process ensures that more glucose is available for fetal growth, as the fetus relies predominantly on glucose for energy during gestation.

Insulin resistance caused by hCS is part of a carefully balanced physiological adjustment that occurs during pregnancy. By decreasing insulin sensitivity, hCS allows the mother to mobilize energy stores, which means that more glucose can circulate in the maternal bloodstream. This adjustment is particularly important as the demand for glucose increases with fetal growth.

Thus, the impact of human chorionic somatomammotropin on insulin is characterized primarily by causing insulin resistance, making option C the accurate choice in understanding its role in maternal-fetal physiology.