Grave’s disease or Basedow’s disease is due to

The correct option is Hyperactivity of thyroid gland.

Let's understand the medical condition known as Grave's disease (or Basedow's disease) step-by-step:
Grave's disease is an autoimmune disorder that primarily affects the thyroid gland, which is a butterfly-shaped endocrine gland located in the neck.

In this condition, the body's immune system produces abnormal antibodies called thyroid-stimulating immunoglobulins (TSIs). These antibodies mimic the action of thyroid-stimulating hormone (TSH), which is normally produced by the pituitary gland to regulate thyroid activity.

Because the TSIs constantly bind to the TSH receptors on the thyroid gland, they stimulate the gland to produce and secrete excessive amounts of thyroid hormones (thyroxine or T₄ and triiodothyronine or T₃). This state of excessive thyroid hormone production and secretion is known as hyperthyroidism or hyperactivity of the thyroid gland.

Symptoms of Grave's disease include weight loss, rapid heartbeat, hand tremors, heat intolerance, anxiety, and sometimes exophthalmos (bulging eyes).

Therefore, Grave's disease or Basedow's disease is caused by the hyperactivity of the thyroid gland.