To the Editor.
—Recently, Nakai et al1 and Odagiri et al2 reported immunoreactive β-endorphin to be present not only in the hypothalamus and pituitary gland but also in the placenta.These results suggest that placental extracts (especially chorionic gonadotropin preparation) may contain immunoreactive β-endorphin as well. We tried to determine immunoreactive βendorphin content in a chorionic gonadotropin preparation (Pregnyl). The content of immunoreactive β-endorphin in the chorionic gonadotropin preparation was demonstrated as 266 pg/5,000 IU of chorionic gonadotropin per ampule. However, the dilution curve of the chorionic gonadotropin preparation didnot show a parallelism with the standard curve of β-endorphin. Odagiri et al2 also observed nonparallelism in the dilution curves of the placental extracts-1M acetic acid, glacial acetic acid, glacial acetic acid/acetone, and Payne's extraction procedures,3 although parallelism was found with water extract of placenta.The analgesic effect of the chorionic gonadotropin preparation was clearly observed in our patients
Hashimoto T, Sawai T. Chorionic Gonadotropin Preparation as an Analgesic. Arch Intern Med. 1981;141(2):269. doi:10.1001/archinte.1981.00340020131038