Assay of Human Growth Hormone in Pregnancy at Parturition and in Lactation. Detection of a Growth-hormone-like Substance from the Placenta.

The metabolic and growth changes associated with pregnancy have stimulated interest in the assay of human growth hormone during pregnancy. Until recently no suitable method for the assay of this hormone in the circulation of normal subjects has been available. Methods, reported to be specific for human growth hormone and sensitive enough to give reliable estimates of the concentration of this hormone in the plasma of normal adults, have now been developed (Hunter and Greenwood, 1962, 1964b; Glick, Roth, Yalow, and Berson, 1963). The importance of the timing of plasma samples for human growth-hormone assay in relation to meals (Greenwood, Hunter, and Marrian, 1964) and to changes in the level of blood sugar (Roth, Glick, Yalow, and Berson, 1963a, 1963b; Hunter and Greenwood, 1964a) has recently been shown. Preliminary studies of the growth-hormone concentration in maternal and neonatal plasma at delivery showed that abnormally high levels of the hormone were present at that time (Hunter and Greenwood, 1962). The results reported here show that the levels of human growth hormone are above normal in lactation, markedly elevated in the foetus, and may be high throughout pregnancy. The assay has detected an additional factor in the maternal circulation during pregnancy and in the placenta at term which is immunologically similar to pituitary growth hormone. This appears to be identical with a human placental lactogen reported by Josimovich and Maclaren (1962) and by Josimovich, Atwood, and Goss (1963).