Abstract
SUMMARY: The gonadotrophic fraction, GA, from the urine of various human subjects, when tested biologically, showed a wide range of potency. Potency was high in cases when high gonadotrophin excretion was likely; it was depressed by oestrogens. It is suggested that GA is a protein vehicle, loaded with variable amounts of gonadotrophic material and that its potency may reflect the concentration of gonadotrophin in the body.