Hypopituitarism overview
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief:
Overview
Hypopituitarism is a medical term describing the deficiency (hypo) of one or more hormones of the pituitary gland. The hypothalamus regulates pituitary secretion by the production of releasing hormones and posterior pituitary hormones and hence its dysfunction can also lead to hypopituitarism.
In endocrinology, deficiency of one or multiple hormones of the anterior pituitary is generally referred to as hypopituitarism, while deficiency of the posterior lobe generally only leads to central diabetes insipidus. The deficiency of all anterior pituitary hormones is termed panhypopituitarism.
Historical Perspective
Discovery of the hypopituitarism returns back to 1914 when Dr. Simmonds described the disease for the first time. The diagnosis has been based on the patients' presentation only since then till 1950 when Dr. Yalow and Berson discovered the radioimmunoassay which helped in the measurement the hormonal levels. Through the 20th and 21st centuries, causes of the hypopituitarism were being described.
Classification
Hypopituitarism can be classified according to the site of the affected part of the pituitary gland either anterior or posterior. It can be also classified according to the etiology into primary or secondary. Based on the gland involvement, hypopituitarism can be classified into partial and panhypopituitarism.
Pathophysiology
Hypopituitarism is believed to be caused mainly due to ischemia of the pituitary gland. This ischemia can be due to hemorrhage, tumors, or brain injury. Compression of the blood vessels is one of the mechanisms that cause ischemia to the pituitary gland and leads to hypopituitarism. Pituitary adenomascause compression to the hypophyseal vessels leading to interruption in the pituitary gland function. Traumatic brain injury either primary or secondary also leads to pituitary gland dysfunction.
Causes
Hypopituitarism causes can be classified based upon the etiology such as congenital or acquired. Congenital causes include idiopathic, anatomic lesion in the sella turcica, and CNS malformations. Common causes among acquired causes include pituitary macroadenoma, craniopharyngioma, surgery,radiation, traumatic brain injury, Sheehan's syndrome, apoplexy, SAH, meningitis, hypophysitis, meningioma, lymphoma, hemochromatosis and Wegner'sgranulomatosis. Less common causes include Peri-natal insults, genetic causes, such as Kallman syndrome, Pallister-Hall syndrome and Rieger syndrome, trauma and pituitary hypoplasia or aplasia. Hypopituitarism can be classified based upon the anatomical location of the pathology such ashypothalamus or pituitary gland.
Differentiating Hypopituitarism from Other Diseases
Hypopituitarism must be differentiated from Sheehan's syndrome, lymphocytic hypophysitis, pituitary apoplexy, hypothyroidism, Addison's disease, empty sella syndrome, hypogonadotropic hypogonadism, Simmonds' disease, hypoprolactinemia, and menopause.
Epidemiology and Demographics
There is no enough information regarding the epidemiology of hypopituitarism and it was only one study combining two cross-sectional studies performed regarding hypopituitarism epidemiology
Risk Factors
Hypopituitarism has a big variety of risk factors that increase the possibility of acquiring the disease. These risk factors incluide pituitary tumor, brain injury, head trauma, genetic defects, and brain surgery.
Screening
Screening of hypopituitarism has been recommended for the patients with traumatic brain injury and patients with a history of radiation exposure on the head.
Natural History, Complications, and Prognosis
The natural history of hypopituitarism depends on the different clinical manifestations. If hypogonadism is left untreated, it will lead to decrease bone density and osteoporosis. Vasopressin deficiency will end up to dehydration and electrolyte imbalance. Complications of hypopituitarism include adrenal crisis, pseutomor cerebrii, and diabetes mellitus. Hypopituitarism has a good prognosis as long as the hormonal replacement therapy is performed properly.
Diagnosis
History and Symptoms
A positive history of head trauma or any mass adenoma) or a lesion ( such as a sellar lesion) or any symptom related to pituitary hormonal deficiency is suggestive of hypopituitarism. Patients of hypopituitarism may be asymptomatic or show symptoms which can be nonspecific or specific for the deficient hormone.