So pituitary gland is called the master gland because it secretes tropic hormones which control the hormone secretions from rest of the endocrine glands.
Hormones secreted from the pituitary gland help control the following body processes:
Growth (GH)
Blood pressure
Some aspects of pregnancy and childbirth including stimulation of uterine contractions during childbirth (Parturition)
Breast milk production
Sex organ functions in both males and females
Thyroid gland function
The conversion of food into energy (metabolism)
Water and osmolarity regulation in the body
Water balance via the control of reabsorption of water by the kidneys