Endocrinology

Answer 7 Exogenous thyrotoxicosis. Exogenous thyrotoxicosis refers to excessive thyroid hormone from an extrathyroidal source. Specifically, thyrotoxicosis factitia describes thyrotoxicosis that is a result of excessive ingestion of thyroid hormone.10 The herbal weight loss supplement that this patient was taking was found to contain both T3 and T4. Patients with exogenous thyrotoxicosis can present similarly to those with hyperthyroidism from other causes.11 Results of this patient’s RAIU and scan demonstrate that both Graves’ disease and toxic multinodular goiter are unlikely, as increased uptake in a homogenous or heterogeneous pattern, respectively, would be expected. The serum thyroglobulin level may help differentiate between endogenous (associated with elevated thyroglobulin) and exogenous (associated with decreased or undetectable thyroglobulin) hyperthyroidism. Hashimoto’s thyroiditis is typically not associated with symptoms of thyrotoxicosis. REFERENCE 10. Ohye H, Fukata S, Kanoh M, et al. Thyrotoxicosis caused by weight-reducing herbal medicines. Arch Intern Med 2005;165:831-4. 11. Cohen JH, Ingbar SH, Braverman LE. Thyrotoxicosis due to ingestion of excess thyroid hormone. Endocr Rev 1989;10:113-24.. Click here to return to the questions

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