Thyrotoxicosis Secondary to Gestational Trophoblastic Disease: A Rare Complication With Clinical Relevance.

Thyrotoxicosis is a clinical syndrome defined by excessive exposure to circulating thyroid hormones, primarily triiodothyronine (T3) and thyroxine (T4). Its most common cause is hyperthyroidism, which is characterized by the increased production and secretion of hormones by the thyroid gland. However, it can also originate from extrathyroidal stimulation. An example is the disproportionately high production of human chorionic gonadotropin (HCG) in gestational trophoblastic disease (GTD), where excessive levels of this hormone induce thyrotoxicosis through cross-activation of thyroid-stimulating hormone (TSH) receptors. We present the case of a 23-year-old woman with a history of ectopic pregnancy who presented with persistent pregnancy symptoms. Clinical and laboratory studies confirmed GTD complicated by thyrotoxicosis, evidenced by markedly elevated levels of HCG, suppressed TSH, and elevated free T4. The imaging studies were consistent with an invasive mole with pulmonary metastasis. Management included antithyroid therapy with methimazole (thionamide), beta-blockers, and systemic chemotherapy, given the characteristics of the neoplasm. This case highlights the importance of a multidisciplinary approach in rare conditions such as GTD associated with thyrotoxicosis, where endocrine stabilization and targeted chemotherapy are the fundamental pillars for optimizing clinical and oncological prognosis.