Steroid determination in milk by enzyme immunoassay (EIA).

A simple and sensitive enzyme immunoassay for progesterone using a homologous system was developed covering the range of 30-3000 fmol/test tube (9.4-944 pg) and applied to extracts from milk fat and bovine serum. By changing the incubation procedure the sensitivity of the assay was increased to measure milk from cows directly without extraction. The influence of milk fat is tolerable and does not falsify physiological results concerning corpus luteum activity or inactivity. The EIA can also be used to follow the change of progesterone under physiological, pathological and therapeutic conditions in samples of human blood and saliva after extraction and in serum directly.