SFEBES2025 Poster Presentations Reproductive Endocrinology (22 abstracts)
When supplements mislead: elevated testosterone level in a patient on high dose biotin
Prethivan Pillai Gopalakrishnan , Amit Banerjee , Heather Sullivan , Mohammad Al-Jubouri , Samuel J Westall , Ei Thuzar Aung , Tala Balafshan , Sid McNulty , Niall Furlong , Prakash Narayanan & Sumudu Bujawansa
Whiston Hospital, Prescot, United Kingdom
A 39-year-old-lady was referred to the endocrinology clinic after presenting to her GP with lethargy, where routine bloods found raised testosterone 5.5 nmol/l (Ref range 0.3 - 1.2) and free androgen index 7.9% (Ref 0.3 - 4.4), with LH <1.5 IU/L and FSH 2.4 IU/l. Otherwise, SHBG, prolactin, TSH and IGF-1 levels were normal. Her menses were regular and she did not have hirsutism, female pattern hair loss, acne, overt virilisation, Cushingoid features or weight loss. A thorough medication history revealed consumption of high dose biotin (10g/day for the past 3 months), leading to a suspicion of biotin induced immunoassay interference. Biotin was discontinued and testosterone levels normalised (0.8 nmol/l) a month later with normal LH (9.2 IU/l) and FSH (5.7 IU/l). DHEAS, androstenedione and 17-OHP levels were normal upon testing following discontinuation, but not tested prior. Biotin interference on immunoassay is widely reported for thyroid function, parathyroid hormone, troponin, proBNP and progesterone assays, however not as widely reported for testosterone. Interference in competitive immunoassays is found to take place when biotin is taken at supra-physiological dose. Adequate Intake (AI) for biotin in adults is 30 mcg/day, but can be obtained over-the-counter at higher doses as a purported supplement for nail and hair growth. Biotin’s half-life is 2 hours, and is fully excreted in 5 half-lives. Biotin should be withheld for at least 1-3 days before testing testosterone as the half-life is dependent on the dose and frequency of intake, especially if it is taken ≥5 mg/day. It can be further prolonged in renal impairment as it is renally excreted. This case demonstrates the importance of careful drug history taking in female patients with elevated testosterone prior to proceeding with unnecessary investigations, especially in the absence of clinical features of hyperandrogenism.
Volume 109
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Endocrine Abstracts
ISSN 1470-3947 (print) | ISSN 1479-6848 (online)
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