The Placental Gonadotrophin and Luteal Function in Monkeys (Macaca mulatta) *

Among the gonadotrophins, none has been studied more thoroughly than the active agent present in the blood and urine of pregnant women (Engle"5). Its chemical properties and the biological responses it is capable of inducing have been studied with great thoroughness, but as yet we are in total ignorance concerning the physiological significance of its presence in the pregnant primate. As recently as 1943, an editorial in the Lancet concludes with the remark that, "Chorionic gonadotrophin . .. is interesting as becoming an established active principle with no known function." Whatever the function of this substance may be it is definitely known to be of chorionic origin (Jones, Gey, and Gey22) and therefore should be considered as a hormone of pregnancy, a point that has been emphasized by a number of investigators. This fact places the chorionic gonadotrophin of the human being, and presumably that of the monkey (Hamlett,"6 Delfs11) and chimpanzee (Zuckerman,27 Elder"3), in the same general category of other known placental gonadotrophins such as that of the horse (Catchpole and Lyons,6 Cole and Saunders,7 Day and Rowlands"0), the rat (Astwood and Greep3), and probably the mouse (Newton24) and hamster (Klein'). Sufficient experimental evidence is at hand to show that the placental hormones of the several groups of mammals mentioned differ widely both as to physiological action and chemical properties, yet they are all probably concerned with maintaining the conditions of pregnancy in their respective species (Hisaw and Astwood20). Experimental results give rise to considerable doubt as to whether this hormone from the human chorion should be considered as a gonadotrophin. It does not promote follicular growth in the ovaries of Macaca mulatta or women (Brown, Bradbury, and Metzger4). In fact, its administration brings about follicular atresia and hyalinization associated with blanching of the sexual skin and uterine bleeding in monkeys (Engle"5). However, in women it extends the length of the luteal phase of the menstrual cycle and increases the amount of pregnanediol excreted (Browne and Venning5).