The early clinical diagnosis of pregnancy was greatly aided by the introduction of a laboratory test devised by Zondek and Aschheim in 1928. This test is based on an observation made in 1922 by Long and Evans, who demonstrated that intraperitoneal injections of fresh extract of the anterior lobe of the pituitary body caused an increase in weight of the ovaries of immature rats. Furthermore, large numbers of corpora lutea were formed in these ovaries. A short time later it was clearly established that the anterior pituitary exerted a powerful stimulant effect on the process of lutein cell formation.
Using these fundamental observations of Long and Evans and having demonstrated the presence of large amounts of gonadotropic substance in the urine of pregnant women, Zondek and Aschheim elaborated a technic for the diagnosis of pregnancy, basing their procedure on the detection of gonadotropic substance in the urine. The test involves
URINARY HISTIDINE IN THE DIAGNOSIS OF PREGNANCY. JAMA. 1936;106(26):2240–2241. doi:10.1001/jama.1936.02770260034012
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