Endocrine Abstracts

Mineral-rich baths and other spa treatments are popular and are promoted as providing a sense of well-being and detoxification. However, exposure to minerals that are easily absorbed through the skin may have unwanted adverse effects in certain groups of patients. In 2001, a 50-year-old woman was diagnosed with thyrotoxic Graves’ disease. Her thyroid peroxidase antibodies were >1000 IU/ml. She was treated with block and replace therapy for 1 year. She remained euthyroid on followup.

In August, 2004, she went to a health spa and spent 1 hour in a flotation tank. The flotation tank contained minerals including iodine and a sign near the tank warned those with thyroid disease to see a supervisor – she did so. She was told that it was alright to go in – presumably because her thyroid disease was in the past. One month later she had a return of hyperthyroid symptoms and her free T4 was 42.1 (normal range 11.5–23.2 pmol/l), free T3 10.56 (3.5–6.5 pmol/l), and TSH <0.01 mU/l. She was started on Carbimazole, initially 15 mg daily, reduced to 5 mg daily in October, 2004, and then stopped in November, 2004, when she became hypothyroid (FT4 3.6, TSH 81). In late December 2004, she was clinically euthyroid (FT4 10.5, TSH 9.17) and has remained so (FT4 11.9, TSH 5.67).

Exposure to excess iodine has been reported with foods, medication, dietary supplements, topical antiseptics, and iodinated contrast media. To the best of our knowledge, the risk of exposure to excess iodine from mineral-rich baths has not been noted as a source of iodine-induced thyroid dysfunction. Patients with a past, as well as present, history of thyroid disease, and their clinicians, should be aware of this possibility.