Abstract
Hypopituitarism usually has an insidious presentation over weeks to months and often remains clinically silent until a particular stressful event such as a concurrent infection or trauma at which time marked symptoms are evident. The reason for a protracted course until deficiency is clinically evident is due to the slow depletion of pituitary hormones. The end endocrine organs also have other, albeit less effective, ways of dealing with lack of pituitary input (for example non ACTH stimulation of cortisol from the adrenal or constitutive activation of the TSH receptor at a low level in the thyroid). The presentation of hypopituitarism is different from the catastrophic clinical situation such as a hemorrhagic infarct into the pituitary that results in acute pituitary insufficiency and cardiovascular collapse. The latter is referred to as pituitary apoplexy and is discussed in another chapter. The more common presentation is in a patient who slowly develops fatigue and rather nonspecific symptoms.