Over recent years, the numbers of commercially available slimming aids have increased dramatically. Whilst the majority of these aids are harmless, their interaction with normal physiology is either not understood or not brought to the attention of the customer. We report the case of a 45-year-old woman who presented with clinical and biochemical thyrotoxicosis (fT4 31.5 pmol/l, fT3 14.3 pmol/l, TSH <0.02 mIU/l). She had elevated TPO antibodies (51 IU/ml). She denied taking any prescription or homeopathic medication or iodine containing compounds. There was no history of intravenous contrast use.
Her thyroid function settled rapidly suggesting a thyroiditis rather than Graves disease as the underlying cause for her condition.
At her follow up appointment, she asked if she could continue to take an over the counter slimming aid (Tesco slimming aid 60S, one tablet taken three times per day), having started this therapy 4 months previously. She was advised against this. According to the product literature, this slimming aid contains bladderwrack 32 mg. Bladderwrack (Fucus vesiculosus), a commonly used food supplement, is a significant source of iodine. This is known to increase the risk of thyrotoxicosis via the Jod-Basedow phenomenon.
The accompanying product literature advises against using these tablets in the presence of thyroid disease. However, the majority of patients will be unaware of their thyroid status. This case reinforces the need to take a full dietary history in patients with thyrotoxicosis. Furthermore, patients wishing to take over the counter medication should be advised to seek medical advice before doing so.