Final answer:
Human placental lactogen (hPL) is a hormone that prepares the breasts for lactation and alters maternal metabolism to support fetal nutrition. It prevents insulin from working as efficiently, resulting in greater glucose and fat availability for the fetus. hPL also influences maternal appetite and the mobilization of nutrients necessary for fetal growth.
Step-by-step explanation:
The human placental lactogen (hPL), also known as human chorionic somatomammotropin, is a hormone produced by the placenta involved critically in the regulation of maternal and fetal metabolism during pregnancy. Its main functions include preparation of the mammary glands for lactation after childbirth and modulation of maternal metabolic processes to facilitate the supply of nutrients to the growing fetus.
Although prolactin is the primary hormone responsible for milk synthesis, its action is inhibited by estrogen, progesterone, and other placental hormones during pregnancy to prevent premature milk production. The secretion of human placental lactogen increases the availability of glucose and fatty acids for the fetus by decreasing maternal insulin sensitivity and increasing lipolysis. This hormone is also involved in stimulating the mammary glands to produce milk, ensuring that, post-delivery, the newborn has adequate nutrition.
Moreover, hPL plays a role in regulating the maternal metabolic rate and enhances the absorption and availability of nutrients like amino acids and calcium, essential for fetal growth and bone development. The increase in maternal appetite, weight gain, and the mobilization of calcium from maternal bones for fetal use can also be attributed in part to the hormonal changes associated with the production of human placental lactogen during pregnancy.