Endocrine Abstracts

Besides total body irradiation and immunosuppressive drugs, massive iodine supply and stress might participate in thyroid dysfunction, described in 50% of allo-HSCT. We report on a rare case of hypothyroidism related to blocking TRAb. A 55-year-old man was admitted for asthenia, dyspnea, myalgia, 8 kg-weight gain, constipation, dry skin, hoarse voice, recent deafness. He had moon face without any goiter. He had received, 1 year before, an unrelated 9/10 human leukocyte antigen matched allo HSCT for acute myeloid leukemia after chemotherapy including antilymphocyte serum and had achieved full female donor chimerism. He developed an acute graft-vs-host disease (GvHD) grade II 1 month post-transplantation treated with ciclosporine. Laboratory tests showed high blood cholesterol (3.53 g/l–n: 1.5–2.4), triglycerides (2.70 g/l–n: 0.3–1.50), CPK (2623U/l–n<195), TSH (99 mUI/ml; n>3.5) levels as well as antithyroperoxidase (179 U/ml; n>5) and TSH receptor antibodies (TBII: 102 U/l; n<1) levels with undetectable FT₄ and anti-thyroglobulin antibody. The functional study of TBII confirmed high blocking (TRAbs 92%; n<30) and low stimulating (TSAbs 58%; n<125) activities. The immunophenotype showed a lymphopenia with an increased CD4+(48.7%; n:38–46) and low CD8+(28%; n: 31–40) percentages. Indeed, the development of autoimmune hypothyroidism is frequent post allo-HSCT and requires regularly monitoring of TSH, given the difficulty of diagnosis in patients whose complaints can easily be attributed to the causal disease or GvHD. Immunological dysregulation during T-cell engraftment may also favour hyperthyroidism, sometimes preceded by a hypothyroid episode related to blocking TBII, called immune reconstitution syndrome. This rare and delayed syndrome has been reported in children post allo-HSCT (Sinha Thyroid 2013) or HIV (Sheikh AIDS 2014) treatment and coincided with a rapid expansion in naïve and total CD4. TSAbs and TBAbs have been shown to have similar characteristics (high affinity and similar binding epitopes on the TSH-R; morgenthaler JCEM 2007). The occurrence of ‘switching’ emphasizes the need for careful patient monitoring and management.