It modifies the metabolic state of the mother during pregnancy to facilitate energy supply to the fetus.

[2] hPL molecular mass is 22 125 Da and contains single chain consisting of 191 amino acid residues that are linked by two disulfide bonds and the structure contains 8 helices.

[1] hPL is present only during pregnancy, with maternal serum levels rising in relation to the growth of the fetus and placenta.

[6] In addition, hPL has been found to stimulate DNA synthesis in human mammary fibroadenoma cells transplanted into mice, which suggests that hPL promotes the growth of the human mammary gland similarly to prolactin.

[citation needed] Also, normal pregnancies have been reported with undetectable maternal levels of hPL.