As far as i know it´s either you lose / gain weight fast but that´s just one of the symptoms. depende actually sa degree ng hyperthyroidism ang treatment, some can be treated with just hormone therapy(supplements) or by radiation therapy and some by surgery. Usual test to diagnose if you have hyperthyroidism is through blood test (specific for T3, T4 & TSH), kung may makitang abnormality in hormone levels dun sa blood then they will check through palpation & worse ultrasound. One should see an endocrinologist kung talagang gusto but usually blood test is enough and someone who can read/interpret the results for you. Good luck po!