Testosterone, cortisol, prolactin and bioactive luteinizing hormone in day and night samples of cerebrospinal fluid and serum of male rhesus monkeys.

Testosterone (T), cortisol (C), prolactin (PRL) and bioactive luteinizing hormone (bLH) were found to be normal constituents of the cerebrospinal fluid (CSF) of all the 15 adult male rhesus monkeys studied. The CSF levels of the hormones showed a good correlation with their serum levels. The geometric mean values of circulating levels of T, PRL, bLH in all the animals studied were significantly lower in the samples of the two body fluids collected between 09.00 and 11.00 h as compared with those collected between 21.00 and 23.00 h. C levels were higher during the day as compared with the night samples. This marked difference between the day and night levels of the circulating hormones was not observed in a few individuals which suggests that the diurnal changes in circulating levels of these hormones may not occur as a rule in all rhesus monkeys. The serum:CSF ratios for C, PRL and bLH did not vary significantly between the day and night samples of the body fluids as they did for T. This suggests that T is poorly transferred from the blood to the CSF as compared with the other 3 hormones studied. The possible pathways by which the hormones are transferred into the CSF and the functional significance of their presence in the CSF are discussed.