Endocrine Abstracts

We describe an interesting case of a man who poses a significant ongoing management challenge. He presented with mild biochemical evidence of T3 thyrotoxicosis (FT3, 8.2, FT4 13.6, TSH 0.02). Carbimazole 20 mg was started and despite increasing dosage, he deteriorated significantly. He was concordant with medication. His TBII and thyroid auto-antibodies were negative. A Tc uptake scan showed reduced uptake. Prednisolone was added, thinking that he may have thyroiditis. Despite continued treatment with Carbimazole and 60 mg of prednisolone, he failed to respond, and underwent thyroidectomy. After a very a short period of euthyroidism post-surgery, he became thyrotoxic and asked as to why this was the case. A re-think of the diagnosis raised doubts about factitious thyrotoxicosis. A radioiodine uptake scan showed no uptake in the thyroid bed or any ectopic thyroid tissue. Review of thyroid histology showed no features of Grave’s disease. We felt that he may be taking exogenous thyroid hormones. He continues to be thyrotoxic and subsequently developed hypogonadism with a suppressed FSH/LH, consistent with exogenous administration of anabolic steroids. The patient denies taking any exogenous medication either known or unknown to him, and continues under endocrine follow-up. We feel that this case is likely to represent a case of severe factitious thyrotoxicosis, on the basis of a poor initial response to high dosage of Carbimazole and Prednisolone; lack of biomarkers of autoimmune thyroid disease. No evidence of Graves’ disease or other thyroid pathology on review of histology. A negative RAI uptake scan post-surgery and an undetectable thyroglobulin; Continuing thyrotoxicosis despite having no thyroid tissue.

Conclusions: Factitious thyrotoxicosis is rare in men and this case demonstrates some of the clinical features and challenges of management. This diagnosis needs to be considered when clinical judgment and investigations do not conform to known causes of thyrotoxicosis.