QJM Advance Access originally published online on June 2, 2007
QJM 2007 100(8):533-534; doi:10.1093/qjmed/hcm048
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Necrotizing fasciitis and hypothyroidism
Sir,A 51-year-old man was admitted to hospital with extensive cellulites, dermal excoriation, and a deep-seated abscess in the skin over the perineum, extending dorsally over the lower back. Urgent surgical exploration and debridement was undertaken, which revealed extensive necrotizing fasciitis. Further management consisted of high-dose intravenous antibiotics and debridement (on six different occasions, including the lower abdominal wall, penile tissue, perineal tissue extending to the back, perianal and large areas of lumbar skin, overall approximately 18% of body surface area). The wound was regularly cleaned and dressed with Betadine (iodine)-soaked gauzes. In view of the large open wound dressed with iodine soaks, concern was raised about the possible absorption of iodine through the large surface area, and the potential for this to accumulate in the thyroid gland (the main iodine reserve of the body). Therefore, plasma and urine iodine levels and thyroid function were measured. Plasma and urine iodine were grossly elevated: plasma iodine 87 µmol/l (normal <0.63); urine iodine 372 µmol/l (normal <1.97). Thyroid function tests showed plasma thyroid-stimulating hormone (TSH) 17 mU/l (normal 0.35–5.0) and free thyroxine (FT4) 11.2 pmol/l (normal 11–25) (Table 1). The Betadine dressings were gradually reduced and discontinued, and treatment was commenced with thyroxine 50 mcg/day. Of note, thyroid peroxidase antibodies were normal. Table 1 shows thyroid function with respect to treatment with thyroxine. One month later, plasma and urine iodine concentrations had decreased dramatically (urine iodine 3.58 µmol/l, plasma iodine 0.75 µmol/l). At present (3 months after initial hypothyroidism) he remains on a low dose of thyroxine (50 mcg/day). The likely diagnosis is iodine-induced hypothyroidism, with the Betadine dressings providing the continuous source of iodine.
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In our patient, hypothyroidism resulted from iodine toxicity, as a consequence of iodine-soaked dressings applied to a large open wound. Thyroid hormone synthesis is tightly regulated in the thyroid gland. When iodine is present in excess, this inhibits thyroid hormone synthesis and during prolonged exposure, results in hypothyroidism (the Wolff-Chaikoff effect1). Hypothyroidism resulting from the Wolff-Chaikoff effect is usually transient, and normal thyroid function resumes following removal of the excess iodine source. This case illustrates the importance of awareness of thyroid dysfunction in surgical patients with large open wounds that require regular iodine-based dressings. In the literature, we found only one other report of topical iodine use associated with hypothyroidism:3 in four infants with spina bifida, treated daily with an iodine-containing ointment (Betadine) applied to the spina defect. All infants showed excess urinary iodine concentrations.
Department of Diabetes & Endocrinology
Morriston Hospital
Swansea
UK
email: j.w.stephens{at}swansea.ac.uk
References
1. Vagenakis AG, Downs P, Braverman LE, Burger A, Ingbar SH. Control of thyroid hormone secretion in normal subjects receiving iodides. J Clin Invest (1973) 52:528–32.[Web of Science][Medline]
2. Markou K, Georgopoulos N, Kyriazopoulous V, Vagenakis AG. Iodine induced hypothyroidism. Thyroid (2001) 11:501–10.[CrossRef][Web of Science][Medline]
3. Barakat M, Carson D, Hetherton AM, Smyth P, Leslie H. Hypothyroidism secondary to topical iodine treatment in infants with spina bifida. Acta Paediatrics (1994) 83:741–3.
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