Human Hormones

Human placental lactogen (HPL), also called human chorionic somatomammotropin, is a hormone found in the human body. It is secreted from the synctiiotrophoblast during pregnancy. HPL consists of 190 amino acids that are linked by two disulfite bonds. Its structure is very similar to that of somatotropin. HPL is classified as a peptide hormone.
Structure and Production

HPL is produced in and secreted from the synctiiotrophoblast during pregnancy. It modifies the metabolic state of the mother during pregnancy to facilitate the energy supply of the fetus. HPL is only present during pregnancy with maternal serum levels rising in relation to the growth of the fetus and placenta. Maximum levels are reached near term, typically to 5-7 mg/ml. Higher levels of HPL are noted in patients with multiple gestation. Little HPL enters the fetal circulation.

HPL affects the metabolic system of the maternal organism. HPL increases production of insulin and IGF-1 and increases insulin resistance and carbohydrate intolerance. Chronic hypoglycemia leads to a rise in HPL. HPL induces lipolysis with the release of free fatty acid, increase in insulin secretion, and insulin resistance. With fasting and release of HPL, free fatty acids become available for the maternal organism as fuel, so that relatively more glucose can be utilized by the fetus. Also, ketones formed from free fatty acids can cross the placenta and be used by the fetus. These events support energy supply to the fetus in states of starvation. There is currently no form of synthetic HPL.