What Happens When Pituitary Glands Are Under or Overactive?

The pituitary gland performs a number of biological functions, such as secreting hormones for metabolism and growth, and when pituitary glands are underactive or overactive, their abilities to perform these functions are impaired. There are several causes of overactive and underactive pituitary glands, including tumors, hormone imbalances and endocrine problems.

The pituitary gland's activities are largely regulated by the brain, which instructs the gland to increase or decrease secretion of certain hormones. This gland contains three parts: an anterior section, an intermediate section and posterior lobes. Together, these parts secrete steroid hormones, growth hormones and thyroid-stimulating hormones.

According to the Cleveland Clinic, overactive pituitary glands create certain diseases and disorders, including Cushing's syndrome, acromegaly, prolactinoma and hyperthyroidism. Overactive pituitary glands are attributed to several causes, including benign tumors and occasionally malignant cells.

Hypopituitarism, or an underactive pituitary gland, affects the anterior lobe of the gland. As a result, the anterior lobe loses some or all of its ability to carry out critical functions. According to Johns Hopkins Medicine, symptoms vary depending on which hormones are not being produced by the pituitary gland. The pituitary gland affects the function of several other endocrine organs, and effects of underactive glands may be sudden and severe or onset gradually.