What is the reason of trembling of the hands?

Tremors: A common cause is hereditary familial tremors or essential tremor, but shaking with hands at rest may be indicative of parkinson problems. Some medicines (e.g., divalproex) can cause tremors, and hyperthyroidism could also be considered.

Many causes: Benign familial essential (meaning of undetermined cause) tremor is the commonest form. Other important causes are thyroid disease, anxiety, hepatic malfunction, side effects of medication etc.