{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,10,16]],"date-time":"2026-10-16T08:32:56Z","timestamp":1792139576697,"version":"4.4.0"},"reference-count":31,"publisher":"Wiley","issue":"1","license":[{"start":{"date-parts":[[2024,8,6]],"date-time":"2024-08-06T00:00:00Z","timestamp":1722902400000},"content-version":"vor","delay-in-days":218,"URL":"http:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/100007605","name":"Aarhus Universitet","doi-asserted-by":"publisher","id":[{"id":"10.13039\/100007605","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100009708","name":"Novo Nordisk Fonden","doi-asserted-by":"publisher","award":["NNF20OC0060610"],"award-info":[{"award-number":["NNF20OC0060610"]}],"id":[{"id":"10.13039\/501100009708","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100006197","name":"Fonden til L\u00e6gevidenskabens Fremme","doi-asserted-by":"publisher","id":[{"id":"10.13039\/501100006197","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["onlinelibrary.wiley.com"],"crossmark-restriction":true},"short-container-title":["Journal of Nutrition and Metabolism"],"published-print":{"date-parts":[[2024,1]]},"abstract":"<jats:p><jats:italic>Background<\/jats:italic>. Beta\u2010hydroxybuturate (<jats:italic>\u03b2<\/jats:italic>\u2010OHB) supplements are commonly utilized in sports by both recreational and professional athletes. In a recent study, we observed a drop in testosterone levels following the oral ingestion of racemic sodium\u2010<jats:italic>\u03b2<\/jats:italic>\u2010OHB. In this investigation, we aim to determine whether a single oral dose of ketone ester (study I) and prolonged endogenous ketosis (study II) also reduces testosterone levels. <jats:italic>Design<\/jats:italic>. This investigation integrated samples from two distinct studies. Study I was a randomized, controlled, crossover trial with ten healthy, young male participants receiving either a weight\u2010adjusted ketone ester or control (water, CTR) and vice versa following an overnight fast. Repeated blood sampling was used to monitor plasma <jats:italic>\u03b2<\/jats:italic>\u2010OHB and testosterone levels. Study II, another randomized, controlled, crossover trial, included 11 middle\u2010aged participants (five males). They followed either a ketogenic diet (KD) characterized by low carbohydrates and high fat content or a standard diet (SDD) for three weeks. After each study period, participants underwent examination following an overnight fast, with repeated measures employed to analyze concentrations of plasma <jats:italic>\u03b2<\/jats:italic>\u2010OHB and sex hormone levels. <jats:italic>Results<\/jats:italic>. Study I: Testosterone decreased from 23.8\u2009\u00b1\u20092.4\u2009nmol\/l to 22.3\u2009\u00b1\u20092.5\u2009nmol\/l 300\u2009minutes after the ketone ester and increased from 20.9\u2009\u00b1\u20092.1\u2009nmol\/l to 22.2\u2009\u00b1\u20091.9 300\u2009minutes after CTR. This difference was not significant, <jats:italic>p<\/jats:italic>\u2009=\u20090.06. <jats:italic>Study II<\/jats:italic>. Total testosterone was unaffected after the KD compared to the SDD in men (20.2\u2009\u00b1\u20091.23\u2009nmol\/l vs. 18.2\u2009\u00b1\u20091.23\u2009nmol\/l (<jats:italic>p<\/jats:italic>\u2009=\u20090.1)) and was lower after KD in women (0.87\u2009\u00b1\u20090.06 vs. 1.1\u2009\u00b1\u20090.06\u2009nmol\/l (<jats:italic>p<\/jats:italic>\u2009&lt;\u20090.0001)). Sex hormone\u2010binding globulin (SHBG) increased in men after KD compared with SDD (31.2\u2009\u00b1\u20092.6\u2009nmol\/l vs 25.0\u2009\u00b1\u20092.6\u2009nmol\/l, <jats:italic>p<\/jats:italic>\u2009&lt;\u20090.0001) and women (26.5\u2009\u00b1\u20093.05\u2009nmol\/l vs 24.2\u2009\u00b1\u20093.05\u2009nmol\/l, <jats:italic>p<\/jats:italic>\u2009=\u20090.003). The free androgen index decreased after KD in men (ratio: 0.65\u2009\u00b1\u20090.05 vs. ratio: 0.74\u2009\u00b1\u20090.05, <jats:italic>p<\/jats:italic>\u2009=\u20090.04) and in women (ratio: 0.036\u2009\u00b1\u20090.006 vs. SDD 0.05\u2009\u00b1\u20090.006, <jats:italic>p<\/jats:italic>\u2009=\u20090.0001). Free estradiol index was also found lower after KD in men (ratio: 3.1\u2009\u00b1\u20090.8 vs. ratio: 4.8\u2009\u00b1\u20090.8, <jats:italic>p<\/jats:italic>\u2009=\u20090.0003) and in women (ratio: 1.2\u2009\u00b1\u20092.2 vs. 9.8\u2009\u00b1\u20092.2, <jats:italic>p<\/jats:italic>\u2009=\u20090.0001). <jats:italic>Conclusion<\/jats:italic>. Our findings indicate that the acute ingestion of ketone ester may not reduce testosterone levels in healthy young males. However, a three\u2010week exposure to KB from a KD results in an increase in SHBG in men and women with obesity as well as it lowers free testosterone and estradiol for men and women. We thus present evidence of crosstalk between alterations in a metabolite, <jats:italic>\u03b2<\/jats:italic>\u2010OHB, and the regulation of the hypothalamic\u2010pituitary\u2010gonadal axis from a KD. The clinical impact of this reduction remains to be investigated. This trial is registered with <jats:ext-link xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" xlink:href=\"https:\/\/clinicaltrials.gov\/ct2\/show\/NCT04156477\">NCT04156477<\/jats:ext-link>\u200b and <jats:ext-link xmlns:xlink=\"http:\/\/www.w3.org\/1999\/xlink\" xlink:href=\"https:\/\/clinicaltrials.gov\/ct2\/show\/NCT05012748\">NCT05012748<\/jats:ext-link>.<\/jats:p>","DOI":"10.1155\/2024\/9301369","type":"journal-article","created":{"date-parts":[[2024,8,6]],"date-time":"2024-08-06T07:04:55Z","timestamp":1722927895000},"update-policy":"https:\/\/doi.org\/10.1002\/crossmark_policy","source":"Crossref","is-referenced-by-count":10,"title":["Three Weeks on a Ketogenic Diet Reduces Free Testosterone and Free Estradiol in Middle\u2010Aged Obese Men and Women"],"prefix":"10.1155","volume":"2024","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-9574-0612","authenticated-orcid":false,"given":"Mads","family":"Svart","sequence":"first","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9938-2181","authenticated-orcid":false,"given":"Nikolaj","family":"Rittig","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5772-4494","authenticated-orcid":false,"given":"Thien Vinh","family":"Luong","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0009-0006-6363-7406","authenticated-orcid":false,"given":"Nigopan","family":"Gopalasingam","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4263-1815","authenticated-orcid":false,"given":"Esben Thyssen","family":"Vestergaard","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0144-1305","authenticated-orcid":false,"given":"Lars","family":"Gormsen","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-8041-6994","authenticated-orcid":false,"given":"Esben","family":"S\u00f8ndergaard","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0522-0320","authenticated-orcid":false,"given":"Henrik Holm","family":"Thomsen","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5924-1720","authenticated-orcid":false,"given":"Claus H.","family":"Gravholt","sequence":"additional","affiliation":[],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"311","published-online":{"date-parts":[[2024,8,6]]},"reference":[{"key":"e_1_2_9_1_2","doi-asserted-by":"publisher","DOI":"10.1002\/(SICI)1520-7560(199911\/12)15:6<412::AID-DMRR72>3.0.CO;2-8"},{"key":"e_1_2_9_2_2","doi-asserted-by":"publisher","DOI":"10.1007\/s40279-022-01756-2"},{"key":"e_1_2_9_3_2","doi-asserted-by":"publisher","DOI":"10.1152\/japplphysiol.00791.2022"},{"key":"e_1_2_9_4_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.cmet.2016.07.010"},{"key":"e_1_2_9_5_2","doi-asserted-by":"publisher","DOI":"10.3389\/fphys.2020.613648"},{"key":"e_1_2_9_6_2","doi-asserted-by":"publisher","DOI":"10.1007\/s40279-016-0577-y"},{"key":"e_1_2_9_7_2","doi-asserted-by":"publisher","DOI":"10.1111\/dom.15044"},{"key":"e_1_2_9_8_2","doi-asserted-by":"publisher","DOI":"10.1007\/s12020-022-03195-5"},{"key":"e_1_2_9_9_2","doi-asserted-by":"publisher","DOI":"10.1042\/bst20190240"},{"key":"e_1_2_9_10_2","doi-asserted-by":"publisher","DOI":"10.1210\/er.2018-00020"},{"key":"e_1_2_9_11_2","doi-asserted-by":"publisher","DOI":"10.1210\/jc.2013-2835"},{"key":"e_1_2_9_12_2","volume-title":"Physiology, Testosterone","author":"Nassar G. 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