Pituitary adenomas and dyspituitarism.

Recent studies of the structure and function of pituitary adenomas reveal that the majority are functional and that the commonest type is a prolactin secreting adenoma. Studies of hypothalamic-pituitary function provide evidence to suggest that the adenoma develops following prolonged hypothalamic stimulation of the pituitary gland, and that the clinical dyspituitarism is due to the hypothalamic-pituitary dysfunction and not to pituitary destruction by the adenoma. Pituitary adenomas may be classified into those due to a basic neuroendocrine dysfunction (prolactin secreting, acromegaly, Cushing's disease) and those arising secondary to end-organ failure (TSH and FSH secreting). The former group have APUD characteristics and may form part of a pluriglandular syndrome of apudomas. The persistence of a basic neuroendocrine dysfunction following the surgical removal of an adenoma explains the frequent recurrence of symptoms in patients and indicates a need for continued surveillance and long-term therapy.