Which hormones are primarily responsible for pregnancy-induced insulin resistance?

• A. Placental hormones, including human placental lactogen, progesterone, estrogen, and cortisol, cause insulin resistance.
• B. Insulin resistance during pregnancy is caused by reduced physical activity alone.
• C. Adiponectin is the primary driver of insulin resistance in pregnancy.
• D. Renal glucose reabsorption increases insulin sensitivity.

Answer: (A)

Insulin resistance during pregnancy is driven mainly by the placental hormones that oppose insulin’s action in the mother’s tissues. The placenta releases several hormones, with human placental lactogen playing a central role, and hormones like progesterone, estrogen, and cortisol contributing to the effect. These substances make skeletal muscle and adipose tissue less responsive to insulin, and they promote more glucose production by the liver, while also increasing lipolysis to raise free fatty acids. The net result is higher blood glucose levels in the mother, ensuring more glucose is available for the fetus. The mother’s pancreas usually compensates by secreting more insulin, but if it can’t keep up, glucose intolerance or gestational diabetes can develop.

Physical activity affects insulin sensitivity but does not establish the hormonal cause of this state in pregnancy. Adiponectin generally improves insulin sensitivity, so it’s not the driver of insulin resistance in this context. Renal glucose reabsorption relates to how the kidneys handle glucose, not to the hormonal-mediated resistance seen in pregnancy.