Endocrinology is the study of hormones. At the Saint Louis Zoo we deal primarily with reproductive hormones, such as estrogen, progesterone and testosterone. We have a laboratory in the Endangered Species Research Center and Veterinary Hospital, where assay methods are developed and validated to measure these hormones in a wide variety of species.

In order to help conserve endangered species by reproducing them in zoos, it's sometimes necessary to work out the basic biology of reproduction, or to pinpoint the time of ovulation for assisted reproductive techniques. The endocrinology laboratory can help by following changes in the animals' hormone levels throughout their cycles. In most cases, hormones are measured in the animal's droppings, since these can be collected without handling the animal.

Hormone levels can tell us if an animal is pregnant, so that keepers can be ready for the birth and provide maximum comfort and safety for mother and baby. Sometimes hormonal analysis can tell us why an animal is infertile. This might lead to veterinary treatment to increase chances of reproductive success, or to the management decision to concentrate breeding efforts on other individuals.

Some animals reproduce too readily, and in order to keep them in natural family groups without producing more offspring than we can care for, contraception is necessary. Monitoring hormones can tell us whether the contraceptive is effectively suppressing reproductive cycles.

Very few zoos have the trained staff and necessary equipment to perform extensive lab tests, so the Saint Louis Zoo, as a leader in the conservation community, offers Endocrine Laboratory Services at minimal cost to other zoos and conservation organizations. We have received specimens from species ranging from aardvarks to zebras from zoos across the nation.