Thyreotoxicosis means that there is too much thyroid hormone in the body. Tremor in young patients is a common neurologic complaint. Essential tremor and psychogenic causes are frequently suspected. Tremor may be the presenting sign of endocrine disorders, which can remain undiagnosed for months.34 years old  woman presented to GP in September. She complained about hands tremor, worsened with nervous tension, which she attributed to discontinuation of antidepressants month ago. During examination tremor was not present, no other pathologic findings were found. Neurologic examination revealed no significant abnormalities. Essential tremor was diagnosed. Patient sought care again, in November, with  her neck appeared swollen,  palpitation and fatigue.The thyroid gland was palpably enlarged, tremor of the upper limbs, tachycardia of 130/min were noted. Laboratory findings revealed TSH 0.01. She was reffered to endocrinologist  for futher examination of thyreotoxicosis. She was restarted on tiamazol 20 mg per day, vitamin B6, betablockers.This case highlights the importance of repeated clinical evaluation in patients with persistent or evolving tremor symptoms. Tremor can result from neurological, psychiatric, toxic, or endocrine causes. In a young woman with a history of antidepressant discontinuation, a psychogenic or iatrogenic tremor is often considered most likely. The initial diagnosis of essential tremor was reasonable at first, as no other alarming signs were present.Even when tremor initially appears benign, clinicians must remain vigilant for systemic causes, especially when additional symptoms emerge. Re-evaluation based on current findings rather than prior assumptions can prevent diagnostic delay.Endocrine causes of tremor are often underdiagnosed, especially when patients are initially evaluated in a neurological setting. This case underscores the importance of assessing tremor in the context of the overall clinical picture and not excluding systemic diseases based solely on history or prior assumptions.This case emphasizes that tremor should not be evaluated in isolation. Clinical signs may be dynamic and change over time. Assuming that an initial diagnosis remains valid can lead to overlooking serious conditions. When new symptoms arise the differential diagnosis should be reconsidered. Reassessment of patients with changing symptoms is essential, as new clinical signs may redirect diagnostic reasoning.