{
  "abstract": "Background: The impact of thyroid-stimulating hormone (TSH) variation within the normal reference range on IVF outcomes remains controversial, with prior studies yielding conflicting results.\n\nMethods: We conducted a retrospective cohort study of 878 euthyroid women (TSH 0.25–4.0 µIU/mL) undergoing fresh IVF/ICSI cycles at Al-Hayat Hospital, Iraq (2022–2024). Patients were classified into four groups using k-means clustering of serum TSH values: Cluster 1 (2.9–4.0 µIU/mL), Cluster 2 (2.2–2.8 µIU/mL), Cluster 3 (1.4–2.0 µIU/mL), and Cluster 4 (0.25–1.3 µIU/mL). Clinical, hormonal, and embryological parameters were compared across clusters, and stepwise logistic regression was performed to adjust for confounders.\n\nResults: Clinical pregnancy was achieved in 474/878 women (54%). As expected, women with pregnancy were younger (30.1 ± 5.1 vs. 31.2 ± 5.5 years, p = 0.003) and had lower mean TSH (1.95 ± 0.85 vs. 2.08 ± 0.96 µIU/mL, p = 0.030). Ovarian reserve and response markers were higher in the pregnancy group, including antral follicle count (AFC) (11.3 ± 4.2 vs. 10.4 ± 4.2, p = 0.001), preovulatory follicle count (PFC) (11.9 ± 4.2 vs. 11.0 ± 4.2, p = 0.003), and oocyte yield (10.4 ± 5.0 vs. 9.6 ± 4.8, p = 0.010). Oocyte maturation (80.5 ± 15.5% vs. 76.9 ± 17.1%, p = 0.003) and fertilization rates (88.0 ± 14.0% vs. 84.2 ± 16.9%, p = 0.003) were also significantly higher, while women without pregnancy required more ampoules (41.2 ± 18.8 vs. 36.6 ± 16.5, p < 0.001). Stepwise regression identified age (OR = 0.97, p = 0.059), ampoules (OR = 0.99, p = 0.024), oocyte yield (OR = 1.04, p = 0.014), maturation rate (OR = 1.10, p = 0.002), fertilization rate (OR = 1.06, p = 0.015), and TSH clusters as independent predictors. Cluster 3 (TSH 1.4–2.0 µIU/mL) showed the highest pregnancy rate (58.2%), while Cluster 1 (TSH 2.9–4.0 µIU/mL) had the lowest (42.7%) and was independently associated with reduced odds (OR = 0.53, 95% CI 0.35–0.80, p = 0.0024). Subgroup analysis revealed that unexplained and ovarian factor infertility were most sensitive to thyroid variation, whereas male factor infertility remained stable and PCO cases diverged.\n\nConclusions: K-means clustering revealed that women with higher-normal TSH (Cluster 1: 2.9–4.0 µIU/mL) had independently reduced odds of clinical pregnancy (OR = 0.53, 95% CI 0.35–0.80, p = 0.002) compared with Cluster 3 (1.4–2.0 µIU/mL), challenging the adequacy of a single binary cutoff and supporting individualized, data-driven thyroid assessment in IVF.",
  "abstract_shown": true,
  "affiliations": [
    "German University in Cairo",
    "Biochemistry Department, Faculty of Pharmacy and Biotechnology, German University in Cairo"
  ],
  "article_type": "research article",
  "arxiv": null,
  "author_total": 2,
  "authors": [
    {
      "affs": [
        0
      ],
      "name": "Mohamed M. Amin"
    },
    {
      "affs": [
        0,
        1
      ],
      "name": "SI. Hassanein"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/9pzg88ejczmpv.bib",
  "cited_by": 0,
  "doi": "10.3389/fendo.2026.1856685",
  "fulltext_url": "https://www.frontiersin.org/articles/10.3389/fendo.2026.1856685/full",
  "id": "9pzg88ejczmpv",
  "issns": [
    "1664-2392"
  ],
  "landing_url": "https://www.frontiersin.org/articles/10.3389/fendo.2026.1856685/full",
  "language": "en",
  "licence": "CC-BY-4.0",
  "licence_label": "CC BY 4.0",
  "licence_source": "article",
  "licence_url": "https://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": null,
  "native_subjects": [
    [
      "lcc",
      "RC648-665"
    ],
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      "openalex",
      "2712|Thyroid Disorders and Treatments"
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  "openalex": "W7223286528",
  "pdf_url": "https://www.frontiersin.org/journals/endocrinology/articles/10.3389/fendo.2026.1856685/pdf",
  "pmcid": "PMC13739597",
  "pmid": "42996230",
  "published": "2026-10-23",
  "publisher": "Frontiers Media SA",
  "ris": "https://research.draconitic.com/paper/9pzg88ejczmpv.ris",
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      "native_id": "10.3389/fendo.2026.1856685",
      "source": "crossref",
      "url": "https://www.frontiersin.org/articles/10.3389/fendo.2026.1856685/full"
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      "url": "https://doi.org/10.3389/fendo.2026.1856685"
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  "subjects": [
    {
      "field": "medicine",
      "origin": "openalex:2712|Thyroid Disorders and Treatments",
      "subfield": "endocrinology-metabolism"
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  ],
  "title": "Higher TSH within the normal range is independently associated with reduced IVF clinical pregnancy odds: a K-means cluster analysis challenging the binary cutoff paradigm",
  "title_text": "Higher TSH within the normal range is independently associated with reduced IVF clinical pregnancy odds: a K-means cluster analysis challenging the binary cutoff paradigm",
  "type": "peer-reviewed",
  "updated_at": "2026-11-09T15:20:41Z",
  "url": "https://research.draconitic.com/paper/9pzg88ejczmpv",
  "venue": "Frontiers in Endocrinology",
  "versions": []
}