ECE2021 Eposter Presentations Thyroid (43 abstracts)
Hedi Chaker Hospital, Department of Endocrinology, Sfax, Tunisia
Introduction
The synthetic anti-oestrogen tamoxifen is the endocrine treatment modality most commonly used for therapy of hormone sensitive breastcancer. The influence of tamoxifen on thyroid function has not been fully elucidated.
Observation
A 46-year-old female patient who presented a Graves disease diagnosed 10 years ago. She had a moderate vascular goiter and no ocular signs. She presented firstly a severe hyperthyroidism: an elevated FT4 = 82.5 pmol/l (NR = 1121) and a suppressed TSH = 0.001 UI/l (NR = 044). Thyrotropin receptor antibodies (anti-rTSH) were strongly positive at 23.6 IU/l (NR < 2). The patient was treated with Benzylthiouracil for 3 years followed by voluntary interruption of treatment. The patient was later lost to follow-up. Four years later, she had a suspicious nodule in her left breast. The diagnosis of Invasive ductal carcinoma was confirmed. Tumor extension was negative. The procedure was a tumorectomy and lymph node dissection followed by adjuvant radiochemotherapy. The patient then received an antiestrogen for 5 years. The senological evolution was favourable. During these years, she was in clinical euthyroidism despite stopping all antithyroid treatment. When she stopped taking tamoxifen, she again presented a biologically confirmed severe hyperthyroidism (FT4 = 83 pmol/l, TSH = 0.001). Anti-rTSH antibodies were overtly positive (> 40). A radical treatment was indicated for our patient.
Conclusion
In conclusion, our case suggests that tamoxifen may influence thyroid hormone levels by mechanisms related to its known effect on thyroxine-binding globulin.