[Reversible thrombocytopenia and polyneuropathy: the pleiotropic aspects of hypothyroidism]

Although the relationship between hyperthyroidism and thrombocytopenia is well documented, the relationship between hypothyroidism and thrombocytopenia is less well known. We describe a 69-year-old man with severe hypothyroidism, mild thrombocytopenia and sensorimotor axonal polyneuropathy. After thyroid hormone replacement therapy, he became euthyroid and his platelet count normalized over a period of three months. The thrombocytopenia may have been due to an immunomodulatory effect of thyroid-stimulating hormone (TSH). His neurological complaints disappeared and even though electromyography still showed signs of axonal polyneuropathy, nerve conduction velocities normalized and he had signs of re-innervation. Our case clearly demonstrates that hypothyroidism is a heterogeneous disease. As symptoms may be reversible with thyroid hormone replacement therapy, it should not be overlooked.