The testis-like histology of the interstitial gland is reflected in its testis-like steroidogenic activity. Circulating levels of testosterone in the reproductively inactive females were exceptionally high for any nonpregnant female mammal: T europaea, 0.79-1.44 ng/ml; spotted hyena, 0.400.50 ng/ml; rhesus monkey, 0.20-0.80 ng/ml; Siberian tiger, 0.20-0.70 ng/ml; rat, 0.16-0.18 ng/ml; rabbit, 0.05-0.10 ng/ml; dog, 0.030-0.7 ng/ml; cow, 0.01-0.02 ng/ml. In contrast, during the period of reproductive activity, levels of circulating testosterone returned to within typical female levels of 0.24-0.68 ng/ml. Jimenez et al. found a similar trend in seasonal testosterone levels in T. occidentalis; however, because of high variation between individuals, no clear relationship between reproductively active and inactive animals could be defined. The substantial circulating levels of androstenedi-one observed during both spring and autumn indicate that this steroid may provide a substrate for the metabolic production of testosterone as was observed in vitro. Cheap Diskus Advair
The ovotestes of reproductively inactive females contained, per milligram of gonadal protein, around eight times as much testosterone as the ovotestes from pregnant females, while the increase in ovotestis weight was only around 2-fold. Consequently, the increase in plasma testosterone in reproductively inactive females likely results from both the growth of the interstitial gland and an increased synthesis and secretion of testosterone by the Leydig cells of the interstitial gland.