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What is it?

Adrenal insufficiency is a condition characterized by inadequate production of the adrenal hormones cortisol and aldosterone. The adrenal glands are small organs located on top of each kidney. They consist of an inner layer called the adrenal medulla and an outer layer called the adrenal cortex. Each layer produces several different hormones that control many body systems. Hormone production is regulated by interactions between the hypothalamus, the pituitary gland, and the adrenal glands. If any part of their signaling and feedback system is not working, it can cause major disruptions and illness within the body. Primary adrenal insufficiency, also called Addison’s disease, affects the levels of both cortisol and aldosterone. It is caused by underactive or damaged adrenal glands. Secondary adrenal insufficiency is the result of a pituitary dysfunction and typically affects only cortisol production.

皮质醇是由肾上腺皮质分泌的糖皮质激素，它可以调节糖、蛋白和脂类代谢，调节体内血糖水平，它同时还具有抗炎作用和协助机体对外来应激做出反应。醛固酮是由肾上腺皮质分泌的盐皮质激素，调节电解质与盐类代谢。上述两种激素分泌不足，会造成机体虚弱与脱水，无法维持正常的血压与应激反应。

Addison’s disease affects about 1 to 4 people per 100,000 in the U.S. It is found in patients of all ages and affects both males and females equally. Symptoms of insufficiency may not emerge until about 80% to 90% of the adrenal cortex has been destroyed.

在美国，70％的原发性肾上腺皮质功能不全是由于自身免疫性疾病引起，30％是其他原因，如结核（在全球结核流行地区是肾上腺皮质功能不全的主要原因）、细菌、病毒和真菌感染；肾上腺出血及肿瘤。极少数是由于肾上腺皮质的遗传异常引起。继发性肾上腺皮质功能不全是由于垂体促肾上腺皮质激素（adrenocorticotropic hormone, ACTH）分泌不足所致，ACTH是垂体的信使－它通知肾上腺皮质分泌皮质醇。如果是由于垂体损害， 肿瘤，或者是其他原因引起ACTH分泌不足，会造成皮质醇生成的刺激障碍。当患者突然中断皮质类固醇（如强的松－治疗类风湿性关节炎所用的抗炎药）治疗情况下，会引起继发性肾上腺皮质功能不全。这种治疗会抑制皮质醇的正常分泌，需要几周到几个月才会恢复。继发性肾上腺皮质功能不全时，醛固酮的分泌一般不会受到影响。

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About adrenal insufficiency
  • 体征和症状

    肾上腺皮质功能不全的症状常常不够明确且没有特异性，缓慢发病，发病初期身体在应激情况下可出现症状，然后经过数月逐渐加剧。症状包括：

    • 腹痛
    • 脱发
    • 脱水（只在阿狄森病出现）
    • 腹泻与便秘
    • 眩晕
    • 疲劳
    • 色素沉着（只限于阿狄森病―皮肤色素加深，特别是皱纹处、前额、面部的雀斑或是乳头，嘴唇和直肠部位周围变色）
    • 关节与肌肉疼痛
    • 低血压
    • 低血糖
    • 肌无力
    • 嗜盐癖（阿狄森病）
    • 呕吐
    • 体重减轻

    有时，肾上腺皮质功能不全的体征和症状会突然出现，约25％的肾上腺皮质功能不全患者在诊断时已处于高危状态（称为阿狄森病危象或肾上腺皮质危象），这种危象可以由许多原因造成，如应激、外伤、手术或者严重感染。若不及时治疗会有致命危险。急性肾上腺皮质危象体征和症状包括：

    • Kidney failure
    • Loss of consciousness
    • Low blood pressure
    • Severe pain in the lower back, abdomen or legs
    • Severe vomiting and diarrhea, leading to dehydration
    • Shock
  • Tests

      Symptoms such as hyperpigmentation, weakness, low blood pressure, and salt cravings may cause a doctor to suspect adrenal insufficiency, especially if these symptoms appear to worsen during periods of stress. Laboratory tests are used to determine whether adrenal insufficiency is present, to distinguish between primary and secondary insufficiencies, and to try to determine the underlying cause of the condition. Tests are also ordered to evaluate a patient’s electrolyte balance, glucose level, and kidney function. During an adrenal crisis, they are ordered to determine the severity of the imbalances and to monitor the effectiveness of treatment.

      Laboratory Tests
      Cortisol. Levels normally vary in the blood, peaking in the early morning. If the adrenal gland is either not functioning normally or not being stimulated by ACTH, then cortisol levels will be consistently low. Cortisol levels are used, along with ACTH and ACTH stimulation tests, to help diagnose adrenal insufficiency.

      ACTH. ACTH is a pituitary hormone that signals the adrenal glands to produce cortisol. This test is primarily ordered as a baseline test to evaluate whether or not the pituitary is producing appropriate amounts of ACTH. In a patient with adrenal insufficiency, low ACTH levels indicate secondary adrenal insufficiency, while high levels indicate primary adrenal insufficiency (Addison’s disease). The ACTH test is often ordered along with the ACTH stimulation test.

      ACTH stimulation test. This test involves measuring the level of cortisol in a patient’s blood before and after an injection of synthetic ACTH. If the adrenal glands are functional, cortisol levels will rise in response to the ACTH stimulation. If they are damaged or non-functional, then their response to ACTH will be minimal. This rapid screening test may be ordered along with a baseline ACTH test and, if abnormal, may be followed with a 1 to 3 day prolonged ACTH stimulation test to help differentiate between primary and secondary adrenal insufficiency.

      Aldosterone. Blood or urine aldosterone levels are measured to help diagnose Addison’s disease - to determine whether the adrenal gland is producing aldosterone. If the levels are low, it is another indication that the patient may have a primary adrenal insufficiency.

      Electrolytes. Electrolytes (Sodium, Potassium, Chloride and Carbon dioxide) are measured to help detect and evaluate the severity of an existing electrolyte imbalance and to monitor the effectiveness of treatment. Electrolytes may be affected by many conditions; with Addison’s disease the sodium, chloride, and carbon dioxide levels are often low, while the potassium level may be very high.

      BUN and Creatinine are tests done to monitor kidney function.

      Glucose levels may be very low during an adrenal crisis. Glucose may be ordered in order to help monitor a patient during a crisis.

      Occasionally used tests
      Insulin-induced hypoglycemia test. Occasionally, a doctor will order this test to assist in the detection of adrenal insufficiency. Glucose and cortisol levels are measured at predetermined intervals after an injection of insulin is used to stress the pituitary gland. In healthy people, blood glucose levels fall and cortisol concentrations increase. In those with adrenal insufficiency, cortisol levels will remain low and glucose levels will fall, then recover slowly.

      Renin. Renin activity is elevated in primary adrenal insufficiency because a lack of aldosterone causes increased renal sodium losses. This lowers blood sodium levels and decreases the amount of fluid in the blood (which lowers blood volume and pressure), which in turn stimulates renin production by the kidney.

      21-hydroxylase autoantibodies are sometimes ordered as part of the diagnostic process when autoimmune Addison’s disease is suspected. They are considered a good marker of autoimmune Addison's disease but are not widely used at this time.

      Non-Laboratory Tests
      X-rays may be used to look for calcification on the adrenal cortex that may be due to a tuberculosis infection.CT (computerized tomography) or MRI (magnetic resonance imaging) scans are sometimes used to look at the size and shape of the adrenal glands and the pituitary. The adrenal glands can be enlarged with infections and cancers. With autoimmune diseases and secondary adrenal insufficiency, the adrenal glands are often normal or small in size.

    • Treatments

      There are treatments available for primary adrenal insufficiency but no cure. If the condition is due to an infection, the affected person may regain some adrenal function when the infection resolves. Even when people have extensive and permanent damage to their adrenal cortex, however, they should be able to live healthy, relatively normal lives by replacing the missing hormones and observing a few precautions.

      In the case of secondary adrenal insufficiency, it is very rare for a patient to respond to treatment if the cause is pituitary damage or disease. However, if the underlying condition can be resolved, such as if the insufficiency is due to corticosteroid therapy, cortisol production may eventually resume. Treatment for secondary insufficiency also involves hormone replacement.