Testicular regression syndrome and extremely elevated anti-thyroid antibodies on a patient with large unilateral polycystic renal mass

Vanishing testes syndrome (or bilateral anorchia), as part of 46, XY differences of sex development, may be early detected during life or partial gonadal dysgenesis are discovered during adult years with mild forms of hypogonadism. Testicular regression may have a genetic background, as mutations of steroidogenic factor 1 (SF 1), but it may be potentially related to other syndromes and anomalies as mental retard, renal anomalies, etc. We aim to introduce a complex male case with a long medical history, including late diagnosis of vanishing testes syndrome. This case introduces the challenges of distinguishing between testicular regression syndrome and ectopic testes on an adult male with mild form of hypogonadism. Particularly, the vanishing testes syndrome was associated with a compressive form of chronic thyroiditis of fibrous type, with aggressive elevation of anti-thyroid antibodies including after thyroidectomy, a large apparently benign unilateral multi-cystic mass at kidney level. List of abbreviations: ATG = Anti-thyroglobulin antibodies, cm = centimetre, CT = computed tomography, TPO = Antithyreoperoxidase antibodies, TSH = Thyroid Stimulating Hormone