Graves’ Disease Mimicking Orthostatic Dysregulation in an Adolescent Girl: Findings on Active Standing Tests

Orthostatic dysregulation (OD) is common during adolescence and may present with dizziness, palpitations, fatigue, and difficulty getting up in the morning.These symptoms overlap with those of Graves' disease, making differentiation challenging in some patients.A 14-year-old girl presented with headache, dizziness, palpitations, and difficulty getting up in the morning, with worsening symptoms during standing and walking.An active standing test reproduced her symptoms, including tachycardia, lower-extremity tremor, marked sweating, and nausea, and she was initially considered to have OD.Her resting heart rate was already elevated, and marked orthostatic tachycardia resembling postural orthostatic tachycardia syndrome (POTS) was observed during the test.However, thyroid function tests revealed severe hyperthyroidism, and positive thyroid-stimulating hormone receptor antibodies led to a diagnosis of Graves' disease.Following treatment with methimazole, potassium iodide, and propranolol, her symptoms resolved.Propranolol was discontinued after one month.Repeat orthostatic testing after improvement of thyroid function no longer reproduced her symptoms or marked tachycardia.Graves' disease may therefore mimic not only the clinical symptoms of OD but also POTS-like orthostatic tachycardia during orthostatic testing.Thyroid dysfunction may warrant consideration in patients with OD-like symptoms, particularly when accompanied by resting tachycardia, tremor, increased sweating, or weight loss.