Addison’s disease

Addison’s disease Overview Definition Addison’s disease occurs when the adrenal glands do not produce enough cortisol and, in some cases, aldosterone. There are two types of adrenal insufficiency: primary and secondary. Primary adrenal insufficiency (Addison’s disease) is caused by adrenal gland malfunction. Secondary adrenal insufficiency is much more common than primary adrenal insufficiency and is due to pituitary malfunction and a lack of adrenocorticotrophic hormone (ACTH)1 CPPC c01.tex V2 - 11/18/2015 1:44 P.M. Page 8 ❦ ❦ ❦ ❦ 8 Addison’s disease A Risk factors Addison’s disease has a prevalence of 93–140 per million people and annual incidence of 4.7–6.2 per million people in western populations Differential diagnosis The onset of Addison’s disease is often insidious. Its usual symptoms (such as fatigue, lethargy, weakness and low mood) are non-specific and highly prevalent in the general population, and overlap with many other common conditions, including: ● depression ● chronic fatigue syndrome ● anorexia nervosa ● type 1 diabetes ● gastrointestinal disorders Diagnostic tests About half of patients with Addison’s disease are diagnosed only after an acute adrenal crisis. A diagnosis of Addison’s disease is made by laboratory tests, firstly to determine whether levels of cortisol are insufficient and then to establish the cause. A short Synacthen test is the investigation of choice to confirm or exclude Addison’s disease. 250 micrograms of tetracosactide (an analogue of corticotropin) is administered by intramuscular or intravenous injection and three blood samples for serum cortisol are taken immediately, at 30 minutes and at 60 minutes. A normal response is a rise in serum cortisol level to above 500 nmol/L at 30 minutes or 60 minutes. A level less than 100 nmol/L indicates a high likelihood of adrenal insufficiency. A plasma ACTH concentration should be measured, as a raised concentration will distinguish Addison’s disease from secondary adrenal insufficiency. Once the diagnosis of Addison’s disease is made, further investigations are needed to determine the underlying cause Treatment goals Replacing or substituting the adrenal hormones Treatment options ● Hydrocortisone ● Prednisolone ● Fludrocortisone Pharmaceutical care and counselling1,2 Essential intervention Cortisol is replaced orally with hydrocortisone tablets, usually given once or twice daily. If aldosterone is also deficient, it is replaced with oral doses of fludrocortisone acetate taken once a day. Patients receiving aldosterone replacement therapy are usually advised to increase their salt intake. The doses of each of these medications are adjusted to meet the needs of individual patients Essential intervention The usual replacement dose of hydrocortisone is 15–25 mg/day, given in two or three divided doses. Fludrocortisone is given in a single dose of 50–200 micrograms a day. Doses do not have to be matched to meals so patients can take to suit their lifestyle Secondary intervention Medication may need to be increased (doubled or tripled) during times of stress, infection or injury. This should be given parenterally if a patient cannot tolerate the drug orally. A patient with an acute adrenal crisis needs urgent hospital admission for intravenous fluid, parenteral hydrocortisone and treatment of the precipitating cause CPPC c01.tex V2 - 11/18/2015 1:44 P.M. Page 9 ❦ ❦ ❦ ❦ Adrenaline: nebulised 9 Continued A monitoring There are no objective measures for assessing the effectiveness of treatment. Monitor for signs of: ● Overreplacement: hypertension, thin skin, striae, easy bruising, glucose intolerance, hyperglycaemia, electrolyte abnormalities ● Underreplacement: symptoms of Addison’s disease, including fatigue, postural hypotension, nausea, weight loss and salt craving