Oestrogens, compared to other steroids of testicular origin, in blood plasma of boars.

Oestrogens, testosterone, and 5 alpha-androstenone ('boar taint steroid') were determined in peripheral and spermatic vein blood plasma of boars. Oestrone was the predominant steroid in both the conjugated and the unconjugated fractions of total oestrogens. Concentrations of conjugated oestrogens in peripheral plasma generally are in the range of several nanograms/ml, which is similar to the range of 5 alpha-androstenone and testosterone. Unconjugated total oestrogens are in the lower nanogram-range. These concentrations, however, are still higher than those during the oestrus in sows. Stimulation with hCG led to increased concentrations of peripheral plasma oestrogens, demonstrating their testicular origin. Comparative measurements in spermatic vein plasma and peripheral plasma show that in general the testis has to secrete different amounts of the individual steroid to maintain the appropriate peripheral level. A highly correlated course of all the steroids measured was apparent. This was shown for the diurnal rhythm, the age-related changes and for the increase after application of hCG.