{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,23]],"date-time":"2026-06-23T13:53:16Z","timestamp":1782222796114,"version":"3.54.5"},"reference-count":36,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2026,5,13]],"date-time":"2026-05-13T00:00:00Z","timestamp":1778630400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Nutr."],"abstract":"<jats:sec>\n                    <jats:title>Objective<\/jats:title>\n                    <jats:p>This study evaluated serum vitamin D (VD) levels in women with polycystic ovary syndrome (PCOS) and assessed their association with menstrual cycle characteristics.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>In this cross-sectional study, 449 women diagnosed with PCOS were stratified based on 25-hydroxyvitamin D [25(OH)D] levels: low VD group (&amp;lt;20\u202fng\/mL) and normal VD group (\u226520\u202fng\/mL). Menstrual cycles of 26\u201335\u202fdays were defined as normal; cycles exceeding 35\u202fdays were classified as prolonged. All participants underwent measurements of body mass index (BMI), fasting plasma glucose (FPG), fasting insulin (FINS), and sex hormones.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>\n                      The prevalence of prolonged menstrual cycles was significantly higher in the low VD group (87.2%) compared to the normal VD group (70%) (\n                      <jats:italic>p<\/jats:italic>\n                      \u202f&amp;lt;\u202f0.001). Regression analysis demonstrated an inverse association between VD levels and the risk of prolonged cycles (\n                      <jats:italic>p<\/jats:italic>\n                      \u202f&amp;lt;\u202f0.001). This association remained significant after adjusting for age, BMI, HOMA-IR, and total testosterone. Each 1\u202fng\/mL increase in VD was associated with an 9% reduction in the risk of prolonged cycles. Fitted curves indicated a non-linear relationship between VD levels and the prevalence of prolonged cycles. Inflection point analysis identified VD\u202f=\u202f27.76\u202fng\/mL (approximately 28\u202fng\/mL) as the inflection point. Below this level, the prevalence of prolonged cycles decreased as VD increased; above 28\u202fng\/mL, the prevalence plateaued.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusion<\/jats:title>\n                    <jats:p>In this cross-sectional study, lower vitamin D levels were associated with a higher prevalence of prolonged menstrual cycles among women with PCOS. This association suggests that further investigation into whether maintaining vitamin D levels at or above 28\u202fng\/mL could influence menstrual cycle regularity in this population is warranted.<\/jats:p>\n                  <\/jats:sec>","DOI":"10.3389\/fnut.2026.1785886","type":"journal-article","created":{"date-parts":[[2026,5,13]],"date-time":"2026-05-13T04:45:12Z","timestamp":1778647512000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":0,"title":["Vitamin D levels and prolonged menstrual cycle in women with polycystic ovary syndrome: a cross-sectional study"],"prefix":"10.3389","volume":"13","author":[{"given":"Lijing","family":"Wang","sequence":"first","affiliation":[{"name":"Department of Reproductive Health and Infertility, Zhaoqing Maternal and Child Health Care Hospital","place":["Zhaoqing, China"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1965","published-online":{"date-parts":[[2026,5,13]]},"reference":[{"key":"ref1","doi-asserted-by":"publisher","first-page":"685","DOI":"10.1016\/S0140-6736(07)61345-2","article-title":"Polycystic ovary syndrome","volume":"370","author":"Norman","year":"2007","journal-title":"Lancet"},{"key":"ref2","doi-asserted-by":"publisher","first-page":"41","DOI":"10.1093\/humrep\/deh098.","article-title":"Revised 2003 consensus on diagnostic criteria and long-term health risks related to polycystic ovary syndrome (PCOS)","volume":"19","year":"2004","journal-title":"Hum Reprod"},{"key":"ref3","doi-asserted-by":"publisher","first-page":"54","DOI":"10.1056\/NEJMcp1514916","article-title":"Clinical practice. 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