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.
Physical Examination
Clinical presentation in hypopituitarism depends upon the onset, the severity of hormonal deficiency and the number of deficient hormones. Patients with hypopituitarism are ill appearing and usually look tired. Physical examination of patients with hypopituitarism is usually remarkable for the respective hormonal deficiency and present with features of that specific hormone such as hypothyroidism presents as delayed relaxation of tendon reflexes, bradycardia, coarse skin, puffy facies, and loss of eyebrows. ACTH deficiency can present with postural hypotension, tachycardia, and weight loss.Gonadotropin deficiency may present with breast atrophy, soft testes, and regression of sexual characteristics. Growth hormone deficiency can present with short stature, decreased sweating with impaired thermogenesis, and reduced muscle mass.
Laboratory Findings
A subnormal/reduced concentration of pituitary hormones is diagnostic of hypopituitarism. Corticotropin deficiency is detected by assessing basal cortisol secretion. Patients with intermediate cortisol levels need to be tested for ACTH reserve. There are several tests to check the ACTH reserve. Metyrapone test is preferred over others as it is applicable to all adults with no age restriction and has good correlation with stress related cortisol response. Patients with hypopituitarism are screened for hypothyroidism by measuring thyroxine, total thyroxine (T4) and triiodothyronine (T3) uptake, and free T4. Gonadotropin deficiency is confirmed with low estradiol, low testosterone, and low/normal serum FSH/LH. Growth hormone deficiency is confirmed with provocative tests(Insulin induced hypoglycemia and Arginine and GHRH combination) for GH secretion resulting in subnormal levels of serum GH levels, serum insulin-like growth factor-1 levels lower than the age-specific lower limit of normal and deficiency of more than one pituitary hormones e.g ACTH, TSH, and gonadotropins. ADH deficiency is assessed by water deprivation test and ADH suppression test. Prolactin deficiency can be confirmed by directly measuring prolactin levels on more than 1 occasion as its secretion is episodic but it is not done routinely as it is not clinically significant.
Electrocardiogram
There are no electrocardiogram findings associated with hypopituitarism.
X ray
There are no X ray findings associated with hypopituitarism.
CT scan
CT scan is preferred over MRI for visualization of calcification in a meningioma or a craniopharyngioma. Routine CT is insensitive to the diagnosis unless frank intracranial hemorrhage is present.The pituitary mass may be evident and be hyperdense.
MRI
MRI is the imaging procedure of choice in the diagnosis of hypopituitarism. It is preferred over the CT scan as optic chiasm, pituitary stalk, and cavernous sinuses can be seen in MRI. An MRI lesion needs to be related to clinical and lab findings. The absence of an MRI lesion mostly indicates a non-organic etiology. Cystic lesions, such as Rathke's cleft cysts may have a low-intensity signal on T1-weighted images and a high-intensity signal on T2-weighted images. Meningiomas have a homogenous postcontrast enhancement than pituitary adenomas and have a suprasellar attachment. Hemorrhage into thepituitary gland results in a high-intensity signal on both T1- and T2-weighted images.
Ultrasound
There are no ultrasound findings associated with hypopituitarism.
Other imaging findings
There are no other specific imaging findings for hypopituitarism.
Other diagnostic studies
There are no other diagnostic findings for hypopituitarism.