{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,8,27]],"date-time":"2025-08-27T06:10:13Z","timestamp":1756275013978,"version":"3.44.0"},"reference-count":16,"publisher":"BMJ","issue":"9","content-domain":{"domain":["bmj.com"],"crossmark-restriction":true},"short-container-title":["BMJ Case Rep"],"accepted":{"date-parts":[[2021,8,24]]},"published-print":{"date-parts":[[2021,9]]},"abstract":"<jats:p>Carbamazepine (CBZ) is a medication used commonly in epilepsy. Decreases in free T4 levels simulating central hypothyroidism have been reported, although the clinical significance is still unclear. We present a 24-year-old man with Bardet-Biedl syndrome (BBS) who was found to have isolated biochemical central hypothyroidism. BBS is a ciliopathy occasionally associated with anterior pituitary dysfunction. While taking CBZ for epilepsy, his TSH was 1.73 mIU\/L (reference range: 0.20\u20134.00 mIU\/L) with a low free T4 of 6.6\u2009pmol\/L (reference range: 10.0\u201326.0\u2009pmol\/L). Pituitary MRI was normal. Although treated with levothyroxine initially, his apparent biochemical central hypothyroidism was later recognised as secondary to CBZ drug effect. This was confirmed with a normal free T4 of 12.2\u2009pmol\/L while he was off CBZ and levothyroxine. Despite the association between CBZ and biochemical central hypothyroidism, nearly all patients remain clinically euthyroid. This effect is reversible and recognition could lead to reductions in unnecessary thyroid replacement therapy if CBZ is discontinued.<\/jats:p>","DOI":"10.1136\/bcr-2021-245018","type":"journal-article","created":{"date-parts":[[2021,9,3]],"date-time":"2021-09-03T12:16:06Z","timestamp":1630671366000},"page":"e245018","update-policy":"https:\/\/doi.org\/10.1136\/crossmarkpolicy","source":"Crossref","is-referenced-by-count":2,"title":["Carbamazepine drug effect simulating biochemical central hypothyroidism in a patient with Bardet-Biedl syndrome"],"prefix":"10.1136","volume":"14","author":[{"given":"David","family":"Kishlyansky","sequence":"first","affiliation":[{"name":"Department of Internal Medicine, University of Calgary, Calgary, Alberta, Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Gregory","family":"Kline","sequence":"additional","affiliation":[{"name":"Division of Endocrinology, Department of Medicine, University of Calgary Cumming School of Medicine, Calgary, Alberta, Canada"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"239","published-online":{"date-parts":[[2021,9,3]]},"reference":[{"key":"2025082622365204000_14.9.e245018.1","first-page":"S81","article-title":"A quick review of carbamazepine pharmacokinetics in epilepsy from 1953 to 2012","volume":"18","author":"Tolou-Ghamari","year":"2013","journal-title":"J Res Med Sci"},{"key":"2025082622365204000_14.9.e245018.2","doi-asserted-by":"crossref","first-page":"235","DOI":"10.1111\/j.1600-0404.1983.tb04569.x","article-title":"Serum thyroid hormones and blood folic acid during monotherapy with carbamazepine or valproate. 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