Traditionally assessed by the sleeping/resting pulse rate:

Other clinical features generally become more marked across the grades: weight loss, tremor, sweating, heat intolerance, nervousness, muscle weakness, tachyarrhythmia, and cardiac failure. A pulse during sleep is helpful because it is less influenced by anxiety or exertion.

Do not confuse this with thyroid storm. Thyroid storm is acute decompensated severe thyrotoxicosis, assessed using scoring systems such as Burch-Wartofsky, rather than this simple pulse-based clinical grading.