Endocrinology is the study of hormones—internal chemical messengers that regulate animal physiology and behavior. The Saint Louis Zoo's Endocrinology Lab works to conserve endangered species, both in zoos and in the wild, by studying reproductive and stress hormones. Measuring levels and patterns of these hormones provides insight into an animal's reproductive status and well-being, information that can be used to improve health and reproductive success.

Over the past 20 years, the Endocrinology Lab has developed and validated steroid radioimmunoassays and enzymeimmunoassays for a wide array of species and sample types. In particular, the lab specializes in analyzing hormone levels in fecal, urine and saliva samples. These samples contain much of the same information as blood, with the added advantage of not having to disturb the animal during collection.

The Endocrinology Lab also provides diagnostic services to zoos, universities and conservation organizations at minimal cost.