Addison’s disease, or adrenal insufficiency, is a rare hormonal disorder of the adrenal glands that affects around 8,400 people in the UK.
The adrenal glands are about the size of a pea and perched on top of the kidneys, and affect the body’s production of the hormones cortisol and sometimes aldosterone.
When someone suffers from adrenal insufficiency, those glands aren’t producing a sufficient amount of these hormones. This can have a detrimental effect on someone’s health and well-being. But because the symptoms are similar to a host of other conditions, Addison’s disease can prove tough to isolate.
What to look out for
According to advice provided by the NHS, the symptoms in the early stages of Addison’s disease, which affects both men and women, are gradual and easy to misread as they’re similar to many other conditions.
People can experience severe fatigue, muscle weakness, low moods, loss of appetite, unintentional weight loss, low blood pressure, nausea, vomiting and salt craving.
“Symptoms are often misread or ignored until a relatively minor infection leads to an abnormally long convalescence, which prompts an investigation,” says Professor Wiebke Arlt from the Centre for Endocrinology, Diabetes & Metabolism at the University of Birmingham.
If Addison’s disease is left untreated, the level of hormones produced by the adrenal gland will gradually decrease in the body. This will cause symptoms to get progressively worse and eventually lead to a potentially life-threatening situation called an adrenal, or Addisonian, crisis. Signs include severe dehydration; pale, cold, clammy skin; rapid, shallow breathing; extreme sleepiness; severe vomiting and diarrhoea. If left untreated, it can prove fatal, so the patient should be admitted to hospital as an emergency.
Back to basics
To understand the disorder, it’s important to get to grips with the basics and that means understanding what the adrenal glands are – and so to the science.
“Adrenal glands have an inner core (known as the medulla) surrounded by an outer shell (known as the cortex) ,” explains Arlt.
The inner medulla produces adrenaline, the ‘fight or flight’ stress hormone. While the absence of this does not cause the disease, the cortex is more critical.
“It produces the steroid hormones that are essential for life: cortisol and aldosterone,” he adds.
“Cortisol mobilises nutrients, enables the body to fight inflammation, stimulates the liver to produce blood sugar and also helps control the amount of water in the body. Aldosterone, meanwhile, regulates the salt and water levels, which can affect blood volume and pressure.”
Why does it happen?
The disorder occurs if the adrenal glands are destroyed, absent or unable to function and failure of the glands themselves is known as primary adrenal insufficiency.
“It’s most often caused by autoimmune disease where the body’s immune system mounts an attack against its own adrenal glands,” explains Arlt.
“However it can also be caused by infection, most importantly by tuberculosis and sometimes by both adrenal glands being surgically removed.”
The pituitary effect
Another important cause is any disease affecting the pituitary gland, which is located behind the nose at the bottom of the brain.
“The pituitary is the master gland that tells the other glands in the body what to do,” continues Arlt.
“The pituitary gland produces a hormone called ACTH (adrenocorticotropic hormone to give it its full name), which travels in the blood stream to the adrenal glands.
“Here it acts as a signal, causing the adrenal glands to produce more cortisol. If the pituitary gland stops making ACTH, [then] cortisol production by the adrenals is no longer controlled properly and a condition called secondary adrenal insufficiency arises.”
But in most cases, aldosterone is still produced, which means that people suffering from secondary adrenal insufficiency have fewer problems than those with primary adrenal insufficiency.
Determining a diagnosis
Due to the ambiguous nature of the symptoms, a Short Synacthen Test (SST) needs to be performed in order to diagnose adrenal insufficiency.
“This measures the ability of the adrenal glands to produce cortisol in response to (the pituitary hormone) ACTH,” says Arlt. “When carrying out this test, a baseline blood sample is drawn before injecting a dose of ACTH, followed by drawing a second blood sample 30 to 60 minutes later. Failing adrenal glands will not be able to produce a certain level of cortisol.”
If someone has been conclusively diagnosed with adrenal insufficiency, they should receive adrenal hormone replacement therapy as advised by an endocrinologist, a doctor specialising in hormone-related diseases.
“A normal adrenal gland does not need supplements to function properly and there is no recognised medical condition called ‘adrenal fatigue’,” warns Arlt.
“Either the adrenal gland is fine and needs no treatment or there is adrenal insufficiency due to adrenal or pituitary failure.”
So if in doubt, don’t self-diagnose but book an appointment with your GP.