The radioimmunoassay of human lactalbumin.

A radioimmunoassay has been developed for the measurement of human lactalbumin, using the protein isolated in pure form from breast milk. Under disequilibrium conditions with second antibody separation the system will detect 20 pg of lactalbumin. Lactalbumin is detectable in the serum of approximately a third of normal male subjects; among women theproportion having measurable serum levels is age-related. Very much higher levels are present in the serum of lactating women.