Excreted steroids in primate feces over the menstrual cycle and pregnancy.

Techniques were established for the extraction and measurement of 17 beta-estradiol (E2) and progestins (P4) from feces of Old World primates. Studies were conducted to show the sensitivity of these measures, means of preserving fecal samples in the field, effects of urinary contamination, and means to eliminate these effects. Our results show that excreted steroid measures can be used to distinguish between mid-follicular and luteal phases in the menstrual cycle, and to identify pregnancy by Day 20 of gestation; the steroid measures can also be used to identify ovulatory levels of E2 and to establish the length of the menstrual cycle. Urine was shown to contaminate the fecal sample and to confound the estimate of steroid levels in feces; prolonged storage (less than 6 h) was shown to change the steroid estimate. Both urinary contamination and storage-dependent changes were eliminated by the addition of ethanol to the sample. Preliminary results also suggest that effects of dietary fiber on steroid hormone levels are minimal when controlled quantitatively by adjusting for water content of the fecal sample. We conclude that these measurements of excreted steroids provide a valid, noninvasive measure of physiological state of the hypothalamic-pituitary-ovarian axis among free-ranging animals in the field.