Characterization of Circulating Maternal Progestagens, Estrogens, Androgens and Glucocorticoids During Normal Pregnancy in Belugas (Delphinapterus leucas) Under Human Care

Determining progesterone concentration is currently considered the most reliable hormonal test for pregnancy detection in belugas. In other cetaceans, additional steroid hormones also serve as pregnancy biomarkers. Whether these hormones are useful for beluga pregnancy diagnosis is unknown. The objective of this study was to conduct circulating steroid hormone analysis across normal pregnancy and different reproductive states in the beluga. Serum samples (n = 240) collected from nine females representative of 20 pregnancies (1991–2017) were analyzed using immunoassays for progesterone, progestagens, estradiol, testosterone, androstenedione, and cortisol. Across pregnancy trimesters (early, mid, late), progesterone was highest during early and mid, and decreased slightly during late, but still maintained concentrations above pre- and post-pregnancy levels. Progestagens increased above luteal phase concentrations during early and continued to increase and remained elevated during mid and late. Estradiol and androstenedione increased during mid and late trimesters. Testosterone was higher at all stages of pregnancy (highest at mid and late) compared to other reproductive states. Across gestation, cortisol was only elevated during late pregnancy. The present study established pregnancy profiles for various steroid hormones during normal beluga pregnancy for animals under human care and identified other non-progestagen hormones that may possibly serve as gestational biomarkers in this species.