The hypothalamus is known as the master switchboard because it's the part of the brain that controls the endocrine system. The pituitary gland, which hangs by a thin stalk from the hypothalamus, is called the master gland of the body because it regulates the activity of the endocrine glands.
Reference
https://medlineplus.gov/ency/anatomyvideos/000048.htm
Hypothalamus is not a gland so it cannot be said to be master gland ..Its area below thalamus neurons collection....If master switchboard ... Hypothalamus
Master gland pituitary
Back part of pituitary contains axonal endings from hypo ....So called neurohypophysis....Posterior pituitary....