{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,17]],"date-time":"2026-08-17T11:24:42Z","timestamp":1786965882418,"version":"build-2736575974"},"reference-count":50,"publisher":"MDPI AG","issue":"16","license":[{"start":{"date-parts":[[2026,8,15]],"date-time":"2026-08-15T00:00:00Z","timestamp":1786752000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Animals"],"abstract":"<jats:p>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\u20132017) 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.<\/jats:p>","DOI":"10.3390\/ani16162550","type":"journal-article","created":{"date-parts":[[2026,8,17]],"date-time":"2026-08-17T10:04:36Z","timestamp":1786961076000},"page":"2550","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Characterization of Circulating Maternal Progestagens, Estrogens, Androgens and Glucocorticoids During Normal Pregnancy in Belugas (Delphinapterus leucas) Under Human Care"],"prefix":"10.3390","volume":"16","author":[{"given":"Karen J.","family":"Steinman","sequence":"first","affiliation":[{"name":"SeaWorld & Busch Gardens Species Preservation Laboratory, United Parks and Resorts, SeaWorld California, San Diego, CA 92109, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7791-2428","authenticated-orcid":false,"given":"Gisele A.","family":"Montano","sequence":"additional","affiliation":[{"name":"SeaWorld & Busch Gardens Species Preservation Laboratory, United Parks and Resorts, SeaWorld California, San Diego, CA 92109, USA"},{"name":"United Parks and Resorts, Corporate Zoological Operations, SeaWorld Orlando, Orlando, FL 32821, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Todd R.","family":"Robeck","sequence":"additional","affiliation":[{"name":"SeaWorld & Busch Gardens Species Preservation Laboratory, United Parks and Resorts, SeaWorld California, San Diego, CA 92109, USA"},{"name":"United Parks and Resorts, Corporate Zoological Operations, SeaWorld Orlando, Orlando, FL 32821, USA"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,8,15]]},"reference":[{"key":"ref_1","unstructured":"International Union of Conservation and Nature (2026, May 08). Beluga Whale. Available online: www.iucnredlist.org\/species\/6335\/50352346."},{"key":"ref_2","unstructured":"(2026, August 12). United States Marine Mammal Protection Act. C.F.R. \u00a7 216, Available online: https:\/\/www.ecfr.gov\/current\/title-50\/chapter-II\/subchapter-C\/part-216."},{"key":"ref_3","unstructured":"(2026, August 12). United States Endangered Species Act. 50 C.F.R. \u00a7 402, Available online: https:\/\/www.ecfr.gov\/current\/title-50\/chapter-IV\/subchapter-A\/part-402."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"5567","DOI":"10.33265\/polar.v40.5567","article-title":"The Role of Aquaria in Beluga Conservation and Research","volume":"40","author":"Romano","year":"2021","journal-title":"Polar Res."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"29","DOI":"10.1002\/zoo.20037","article-title":"Reproduction, Growth and Development in Captive Beluga (Delphinapterus leucas)","volume":"24","author":"Robeck","year":"2005","journal-title":"Zoo Biol."},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"59","DOI":"10.1262\/jrd.17066","article-title":"Basal Body Temperature Method for Detecting Ovarian Cycle in the Captive Beluga (Delphinapterus leucas)","volume":"52","author":"Katsumata","year":"2006","journal-title":"J. Reprod. Dev."},{"key":"ref_7","doi-asserted-by":"crossref","unstructured":"Robeck, T.R., Steinman, K.J., Parry, C.B., Gomez, F.M., and Jensen, E.D. (2021). Comparisons of Serum Progesterone and Progestagen Concentrations in Normal and Abnormal Bottlenose Dolphin (Tursiops truncatus) Pregnancy. Front. Mar. Sci., 8.","DOI":"10.3389\/fmars.2021.630563"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"coz071","DOI":"10.1093\/conphys\/coz071","article-title":"Comparing Progesterone in Blubber and Serum to Assess Pregnancy in Wild Beluga Whales (Delphinapterus leucas)","volume":"7","author":"Goertz","year":"2019","journal-title":"Conserv. Physiol."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"coad075","DOI":"10.1093\/conphys\/coad075","article-title":"Estimating Pregnancy Rate from Blubber Progesterone Levels of a Blindly Biopsied Beluga Population Poses Methodological, Analytical and Statistical Challenges","volume":"11","author":"Renaud","year":"2023","journal-title":"Conserv. Physiol."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"113273","DOI":"10.1016\/j.ygcen.2019.113273","article-title":"Comparative Analysis of Steroids in Cyclic and Pregnant Killer Whales, Beluga Whales and Bottlenose Dolphins by Liquid Chromatography Tandem Mass Spectrometry","volume":"285","author":"Legacki","year":"2020","journal-title":"Gen. Comp. Endocrinol."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"98","DOI":"10.1016\/j.ygcen.2018.06.008","article-title":"Longitudinal Profiles of Relaxin and Progestagens During Pregnancy, Pregnancy Loss and False Pregnancy in the Killer Whale (Orcinus orca)","volume":"267","author":"Robeck","year":"2018","journal-title":"Gen. Comp. Endocrinol."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"116","DOI":"10.1016\/j.ygcen.2017.01.023","article-title":"Characterization and Longitudinal Monitoring of Serum Androgens and Glucocorticoids During Normal Pregnancy in the Killer Whale (Orcinus orca)","volume":"247","author":"Robeck","year":"2017","journal-title":"Gen. Comp. Endocrinol."},{"key":"ref_13","doi-asserted-by":"crossref","unstructured":"Steinman, K.J., Montano, G.A., and Robeck, T.R. (2021). Characterization of Circulating Androgens, Cortisol and Estrogens During Normal, Abnormal and False Pregnancy in Bottlenose Dolphins (Tursiops truncatus) Under Managed Care. Front. Mar. Sci., 8.","DOI":"10.3389\/fmars.2021.737926"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"1701","DOI":"10.1016\/j.theriogenology.2010.04.028","article-title":"Deep Intra-uterine Artificial Inseminations Using Cryopreserved Spermatozoa in Beluga (Delphinapterus leucas)","volume":"74","author":"Robeck","year":"2010","journal-title":"Theriogenology"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"469","DOI":"10.1016\/j.theriogenology.2012.02.011","article-title":"The Relationship of Maternal Characteristics and Circulating Progesterone Concentrations with Reproductive Outcome in the Bottlenose Dolphin (Tursiops truncatus) After Artificial Insemination, with and Without Ovulation Induction, and Natural Breeding","volume":"78","author":"Robeck","year":"2012","journal-title":"Theriogenology"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"83","DOI":"10.1016\/j.ygcen.2016.07.010","article-title":"Characterization and Longitudinal Monitoring of Serum Progestagens and Estrogens During Normal Pregnancy in the Killer Whale (Orcinus orca)","volume":"236","author":"Robeck","year":"2016","journal-title":"Gen. Comp. Endocrinol."},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"West, B.T., Welch, K.B., and Galecki, A.T. (2015). Linear Mixed Models: A Practical Guide Using Statistical Software, CRC Press. [2nd ed.].","DOI":"10.1201\/b17198"},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"1309","DOI":"10.1139\/f71-198","article-title":"A Reconsideration of Aspects of Growth, Reproduction and Behavior of the White Whale (Delphinapterus leucas) with Reference to the Cumberland Sound, Baffin Island, Population","volume":"28","author":"Brodie","year":"1971","journal-title":"J. Fish. Res. Board Can."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"195","DOI":"10.7146\/mogbiosci.v39.142550","article-title":"Growth, Reproduction, Age Structure and Feeding Habits of White Whales (Delphinapterus leucas) in West Greenland Waters","volume":"39","author":"Teilmann","year":"1994","journal-title":"Meddelelser Gr\u00f8\u00f8nland Biosci."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"100071","DOI":"10.1016\/j.therwi.2024.100071","article-title":"A Review of Beluga (Delphinapterus leucas) Sexual Behavior and Reproductive Physiology Leading to Conception","volume":"4","author":"Hill","year":"2024","journal-title":"Theriogen. Wild"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"591","DOI":"10.1111\/mms.12180","article-title":"Development of Predictive Models for Determining Fetal Age-at-length in Belugas (Delphinapterus leucas) and Their Application Toward In Situ and Ex Situ Population Management","volume":"31","author":"Robeck","year":"2015","journal-title":"Mar. Mammal Sci."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"1065","DOI":"10.1139\/f73-178","article-title":"Biology of the white whales (Delphinapterus leucas) in western Hudson Bay","volume":"30","author":"Sergeant","year":"1973","journal-title":"J. Fish. Res. Board Can."},{"key":"ref_23","unstructured":"Calle, P.P., Cook, R.A., McClave, C., and Palma, S. (1993, January 24). Circulating Gestational Progesterone and Estradiol Concentrations, Parturition, and Placental Descriptions in Two Beluga Whales (Delphinapterus leucas). Proceedings of the International Association of Aquatic Animal Medicine, Chicago, IL, USA."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"41","DOI":"10.1002\/zoo.1430060106","article-title":"Progress Report: Results of a Long Range Captive Breeding Program for the Bottlenose Dolphin, Tursiops truncatus and Tursiops truncatus gilli","volume":"6","author":"Cornell","year":"1987","journal-title":"Zoo Biol."},{"key":"ref_25","unstructured":"Leatherwood, S., and Reeves, R.R. (1990). Artificial Insemination of Bottlenose Dolphins. The Bottlenose Dolphin, Academic Press."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"417","DOI":"10.1002\/zoo.1430140504","article-title":"Killer Whale (Orcinus orca) Reproduction at Sea World","volume":"14","author":"Duffield","year":"1995","journal-title":"Zoo Biol."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1262\/jrd.09-212E","article-title":"Study on reproduction of captive marine mammals","volume":"56","author":"Katsumata","year":"2010","journal-title":"J. Reprod. Dev."},{"key":"ref_28","doi-asserted-by":"crossref","unstructured":"Sotnikov, D.V., Zherdev, A.V., Zvereva, E.A., Eremin, S.A., and Dzantiev, B.B. (2021). Changing Cross-Reactivity for Different Immunoassays Using the Same Antibodies: Theoretical Description and Experimental Confirmation. Appl. Sci., 11.","DOI":"10.3390\/app11146581"},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"198","DOI":"10.1578\/AM.39.2.2013.187","article-title":"Evaluation of Single-sample Analysis of Progesterone in Combination with Relaxin for Diagnosis of Pregnancy Status in Wild Bottlenose Dolphins (Tursiops truncatus)","volume":"39","author":"Bergfelt","year":"2013","journal-title":"Aquat. Mamm."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"1187","DOI":"10.1016\/j.theriogenology.2014.07.030","article-title":"Relaxin: A Hormonal Aid to Diagnose Pregnancy Status in Wild Mammalian Species","volume":"82","author":"Bergfelt","year":"2014","journal-title":"Theriogenology"},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"701","DOI":"10.1016\/j.fertnstert.2005.02.045","article-title":"Steroid Hormone Levels in Pregnancy and 1 Year Post-partum Using Isotope Dilution Tandem Mass Spectrometry","volume":"84","author":"Soldin","year":"2005","journal-title":"Fertil. Steril."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"399","DOI":"10.1146\/annurev.me.19.020168.002151","article-title":"Endocrine Relations Between Mother and Fetus","volume":"19","author":"Solomon","year":"1968","journal-title":"Annu. Rev. Med."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"171","DOI":"10.1016\/0960-0760(92)90045-K","article-title":"Utilization of Maternal and Fetal Androstenedione for Placental Estrogen Production at Mid and Late Baboon Pregnancy","volume":"41","author":"Waddell","year":"1992","journal-title":"J. Steroid Biochem. Mol. Biol."},{"key":"ref_34","first-page":"608","article-title":"Actions of Fetal and Adrenal Steroid Hormones in Primate Pregnancy","volume":"16","author":"Pepe","year":"1995","journal-title":"Endocr. Rev."},{"key":"ref_35","first-page":"15","article-title":"Estrogens, Corticosteroids and Progestagen Patterns in the Pregnant and Non-pregnant Bottle-nosed Dolphin Tursiops truncatus Following the Intramuscular Administration of NIH-FSH-OVINE-S9","volume":"6","author":"Richkind","year":"1975","journal-title":"J. Steroid Biochem."},{"key":"ref_36","unstructured":"Neill, J.D.A. (2007). Parturition. Physiology and Reproduction, Academic Press."},{"key":"ref_37","first-page":"213","article-title":"Overview of Current Research in Parturition","volume":"86","year":"2006","journal-title":"Exp. Physiol."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"308","DOI":"10.1016\/j.ygcen.2005.02.002","article-title":"Assessing Reproductive Status of Right Whales (Eubalaena glacialis) Using Fecal Hormone Metabolites","volume":"142","author":"Rolland","year":"2005","journal-title":"Gen. Comp. Endocrinol."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"Cox006","DOI":"10.1093\/conphys\/cox006","article-title":"A Right Whale Pootree: Classification Trees of Faecal Hormones Identify Reproductive States in North Atlantic Right Whales (Eubalaena glacialis)","volume":"5","author":"Corkeron","year":"2017","journal-title":"Conserv. Physiol."},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"24","DOI":"10.1016\/j.ygcen.2019.04.004","article-title":"Evaluation of Fecal Hormones for Noninvasive Research on Reproduction and Stress in Humpback Whales (Megaptera novaeangliae)","volume":"280","author":"Hunt","year":"2019","journal-title":"Gen. Comp. Endocrinol."},{"key":"ref_41","doi-asserted-by":"crossref","unstructured":"Wasser, S.K., Lundin, J.I., Ayres, K., Seely, E., Giles, D., Balcomb, K., Hempelmann, J., Parsons, K., and Booth, R. (2017). Population Growth is Limited by Nutritional Impacts on Pregnancy Success in Endangered Southern Resident Killer Whales (Orcinus orca). PLoS ONE, 12.","DOI":"10.1371\/journal.pone.0179824"},{"key":"ref_42","unstructured":"Yehle, K.E. (2022). Fecal Hormone Metabolites as Indicators of Stress in the Southern and Northern Resident Killer Whales (Orcinus orca) Populations in Coastal Waters of British Columbia, Canada. [Master\u2019s Thesis, University of British Columbia]. Available online: https:\/\/open.library.ubc.ca\/soa\/cIRcle\/collections\/ubctheses\/24\/items\/1.0416166."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"421","DOI":"10.1530\/REP-15-0547","article-title":"The Dynamic Steroid Landscape of Equine Pregnancy Mapped by Mass Spectrometry","volume":"151","author":"Legacki","year":"2016","journal-title":"Reproduction"},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"416","DOI":"10.1210\/endo-115-1-416","article-title":"Concentration Increase of Unbound Testosterone in Plasma of the Mare Throughout Pregnancy","volume":"115","author":"Silberzahn","year":"1984","journal-title":"Endocrinology"},{"key":"ref_45","doi-asserted-by":"crossref","first-page":"254","DOI":"10.1016\/0002-9378(95)90210-4","article-title":"Scientific Basis and Therapeutic Regimens for Use of Antenatal Glucocorticoids","volume":"173","author":"Ballard","year":"1995","journal-title":"Am. J. Obstet. Gynecol."},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"127","DOI":"10.1016\/j.ygcen.2018.02.015","article-title":"Fecal Steroid Hormones Reveal Reproductive State in Female Blue Whales Sampled in the Gulf of California, Mexico","volume":"261","author":"Atkinson","year":"2018","journal-title":"Gen. Comp. Endocrinol."},{"key":"ref_47","doi-asserted-by":"crossref","first-page":"260","DOI":"10.1016\/j.ygcen.2006.03.012","article-title":"Analysis of fecal glucocorticoids in the North Atlantic right whale (Eubalaena glacialis)","volume":"148","author":"Hunt","year":"2006","journal-title":"Gen. Comp. Endocrinol."},{"key":"ref_48","doi-asserted-by":"crossref","first-page":"392","DOI":"10.1542\/peds.2004-2783","article-title":"Comparison of Infasur (Calfactant) and Survanta (Beractant) in the Prevention and Treatment of Respiratory Distress Syndrome","volume":"116","author":"Bloom","year":"2005","journal-title":"Pediatrics"},{"key":"ref_49","doi-asserted-by":"crossref","first-page":"193","DOI":"10.1638\/2011-0161.1","article-title":"Management of Twin Pregnancy and Neonatal Concerns in a Beluga (Delphinapterus leucas)","volume":"43","author":"Osborn","year":"2012","journal-title":"J. Zoo Wildl. Med."},{"key":"ref_50","doi-asserted-by":"crossref","first-page":"863","DOI":"10.1093\/icb\/28.3.863","article-title":"Energy Allocation in Mammalian Reproduction","volume":"28","author":"Gittleman","year":"1988","journal-title":"Am. Zool."}],"container-title":["Animals"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2076-2615\/16\/16\/2550\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,8,17]],"date-time":"2026-08-17T10:31:45Z","timestamp":1786962705000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2076-2615\/16\/16\/2550"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,8,15]]},"references-count":50,"journal-issue":{"issue":"16","published-online":{"date-parts":[[2026,8]]}},"alternative-id":["ani16162550"],"URL":"https:\/\/doi.org\/10.3390\/ani16162550","relation":{},"ISSN":["2076-2615"],"issn-type":[{"value":"2076-2615","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,8,15]]}}}