Definition:

Hypopituitarism is a chronic endocrine illness, and is the partial or complete insufficiency of anterior pituitary hormone secretion. Anterior pituitary is composed of five cell types that secrete growth hormone (GH), prolactin (PRL), follicle-stimulating hormone (FSH) and luteinizing hormone (LH), thyroid stimulating hormone (TSH) and corticotropin hormone (ACTH). Clinical manifestations of hypopituitarism are variable, often insidious in onset and dependent on the degree and severity of hormone deficiency. However, it is associated with increased mortality and morbidity. A variety of diseases may cause hypopituitarism and, accordingly, this disorder can be divided into two types depending on its cause. Primary hypopituitarism is caused by disorders of the pituitary gland itself and may be due to the loss, damage, or dysfunction of pituitary hormone-secreting cells. On the other hand, secondary hypopituitarism is the result of diseases of the hypothalamus or pituitary stalk interrupting the nerve or vascular connections to the pituitary gland, thereby reducing the secretion of the pituitary hormones. Hypopituitarism can be easily diagnosed by measuring basal pituitary and target hormone levels. MR imaging of the hypothalamo-pituitary region may provide essential information. The most common causes of primary hypopituitarism are pituitary adenoma and complications from surgery or radiation therapy for the treatment of pituitary adenoma. In rare cases, hypopituitarism has been observed when the infection occurs. Sheehan's syndrome is hypopituitarism caused by the postpartum hemorrhage of the pituitary gland. In still rarer cases, solitary or complicated pituitary hormone deficiency syndromes may occur due to genetic causes and typically affect children. The treatment of hypopituitarism typically involves a replacement of the deficient hormone but care must be taken because several studies have reported an increased incidence of cardiovascular disorders and number of deaths among these patients.