Answer:
It would be thyroid gland, as post thyroidectomy an individual can lead a normal life. The thyroid gland is accountable for generating two essential hormones, that is, triiodothyronine and thyroxine. These hormones monitor the metabolism, however, with the application of medications like levothyroxine one can substitute the functioning of the thyroid gland and may lead a normal life.
The pituitary gland is the most essential gland in the body, it is also known as the master gland as the hormones produced by pituitary gland also monitor the functions of other endocrine glands.