Secondary adrenal insufficiency overview

# Overview
Adrenal insufficiency is a condition in which the adrenal glands, located above the kidneys, do not produce adequate amounts of steroid hormones, primarily cortisol, but may also include impaired aldosterone production (a mineralocorticoid) which regulates electrolytes mainly sodium and potassium along side with water retention. Craving for salt or salty foods due to the urinary losses of sodium is common.
Adrenal insufficiency can also occur when the hypothalamus or the pituitary gland, both located at the base of the skull, does not make adequate amounts of the hormones that assist in regulating adrenal function. This is called secondary adrenal insufficiency and is caused by lack of production of ACTH in the pituitary or lack of CRH in the hypothalamus. Accordingly, it is classified in to 2 types, primary adrenal insufficiency and secondary adrenal insufficiency. It must be differentiated from other diseases that may cause hypotension, fatigue, and skin pigmentation. The most potent risk factor in the development of secondary adrenal insufficiency is infections, such as Tuberculosis. Its common complications include hypoglycemia, adrenal crisis,hypovolemic shock and cardiac arrest. Prognosis is generally good in patients with secondary adrenal insufficiency as long as they are on life-time hormonal therapy. The most common symptoms of secondary adrenal insufficiency include Chronic fatigue, weight loss, and visual field defects. The main stay of treatment for secondary adrenal insufficiency is treating the underlying cause. For symptomatic cases, hydrocortisone should be administered. The long-term treatment goal is to maintain normal blood pressure, blood glucose, fluid volume, and a sense of well-being in the patient.

# Historical Perspective
Suprarenal glands were discovered by Eustachius in 1563 and were named as Glandulae renis incumbentes. 35th USA President John F. Kennedy had primary Adrenal insufficiency (Addison's disease).

# Classification
Adrenal insufficiency is classified into 2 types based on the level of impairment, primary adrenal insufficiency and secondary adrenal insufficiency.

# Pathophysiology
Secondary adrenal insufficiency is caused by the processes occurring outside adrenal glands: pituitary causes, drugs, genetic causes.These disease processes causes the decreased production of adrenocorticotrophic hormone (ACTH).

# Causes
Secondary adrenal insufficiency is caused mainly by 4 categories, hypopituitarism, drugs, genetic and other causes. Life-threatening causes include acute withdrawal of steroids, adrenal hemorrhage, Waterhouse-Friderichson syndrome, anti-coagulation and gastroenteritis which causes adrenal crisis. The common causes include chronic steroid therapy and its withdrawal, opiates, causes of pan-hypopituitarism and the less common causes are genetic causes which include combined pituitary hormone deficiency (CPHD), proopiomelanocortin deficiency POMC and isolated ACTH deficiency.

# Differentiating Adrenal Insufficiency from other Diseases
Secondary adrenal insufficiency must be differentiated from primary adrenal insufficiency, acute adrenal insufficiency/adrenal crisis, adrenal hemorrhage, congenital adrenal hyperplasia and salt losing nephropathy based on clinical features, such as fatigue and weight loss and laboratory findings.

# Epidemiology and Demographics
The prevalence of secondary adrenal insufficiency is approximately 15-28 per 100,000 individuals worldwide more common than Addison disease. The incidence increases with age; the median age at diagnosis is 60 years. There is no racial predilection.Women are more commonly affected by secondary adrenal insufficiency than male.

# Risk Factors
The most potent risk factor in the development of secondary adrenal insufficiency is infections, such as Tuberculosis. Other risk factors include genetic defects of adrenal gland, diabetes, and Vitiligo.

# Screening
There is insufficient evidence to recommend routine screening for secondary adrenal insufficiency.

# Natural History, Complications and Prognosis
If left untreated, secondary adrenal insufficiency can be life-threatening. Any stressful event or illness can cause a sudden worsening of symptoms, which can lead to severe dehydration and fatally low blood pressure and eventually death from adrenal crisis.Common complications include hypoglycemia, adrenal crisis,hypovolemic shock and cardiac arrest. Prognosis is generally good in patients with secondary adrenal insufficiency as long as they are on life-time hormonal therapy. Patients with secondary adrenal insufficiency must be closely monitored for compliance with medications as acute cases can be life-threating and the mortality rates can go up to 95% in acute crisis.

# Diagnosis

## History and Symptoms
The most common symptoms of secondary adrenal insufficiency include chronic fatigue, weight loss, and visual field defects.

## Physical Examination
Patients with secondary adrenal insufficiency usually appear weak or cushingoid (if the cause is glucocorticoid withdrawal). Physical examination of patients with secondary adrenal insufficiency is usually remarkable for cushingoid features like muscle weakness, buffalo hump. Hypotension may or may not be present. The absence of hyperpigmentation is the hallmark and a distinguishing feature of secondary adrenal insufficiency. Also, the presence of visual field defects like bitemporal hemianopsia indicates a pituitary tumor.

## Laboratory Findings
Laboratory findings consistent with the diagnosis of adrenal insufficiency may include eosinophilia,lymphocytosis,normocytic anemia,hyponatremia , mild hypercalcemia, and azotemia. Secondary adrenal insufficiency may be confirmed by dynamic tests such as insulin tolerance test and corticotropin stimulation test (standard and low dose). Adrenal function can be assessed by measuring basal ACTH secretion and ACTH reserve (via Metyrapone stimulation test).

## Electrocardiogram
There are no ECG findings associated with secondary adrenal insufficiency.

## Chest X Ray
There are no x-ray findings associated with secondary adrenal insufficiency.

## CT
CT findings suggestive of chronic adrenal insufficiency may include small and atrophic adrenal gland. CT head findings suggestive of pituitary disorder leading to adrenal insufficiency may include hemorrhage in case of pituitary apoplexy or a mass suggestive of pituitary adenoma or craniopharyngioma.

## MRI
MRI is the diagnostic imaging modality used in secondary adrenal insufficiency to assess hypothalamic pituitary adrenal axis. MRI findings suggestive of pituitary abnormality may include a mass suggesting a tumor or empty sella leading to hypopituitarism.

## Echocardiography or Ultrasound
There are no ultrasound findings associated with secondary adrenal insufficiency

## Other Imaging Findings
There are no other imaging findings associated with secondary adrenal insufficiency.

## Other Diagnostic Studies
There are no other diagnostic studies associated with secondary adrenal insufficiency.

# Treatment

## Medical Therapy
The mainstay of treatment for secondary adrenal insufficiency is treating the underlying cause. For symptomatic cases, hydrocortisone should be administered. The long-term treatment goal is to maintain normal blood pressure, blood glucose, fluid volume, and a sense of well-being in the patient.

## Surgery
The mainstay of treatment for secondary adrenal insufficiency is medical therapy. Surgery is usually reserved for tumor of the pituitary which is causing secondary adrenal insufficiency due to mass effect and is resistant to medical therapy.

## Primary Prevention
There are no established measures for the primary prevention of secondary adrenal insufficiency. However, the risk can be minimized by preventing hypopituitarism by good obstetric care and minimizing radiation exposure as hypopituitarism is the main cause of secondary adrenal insufficiency. The other effective measures are tapering of steroids and avoidance of the long-term use of opioids.

## Secondary Prevention
Effective measures for the secondary prevention of secondary adrenal insufficiency include patient and family members education about risks of hormone replacement therapy and dose adjustments during periods of acute illnesses.