Cushing’s disease is a disorder characterised by increased adrenocorticotropic hormone (ACTH) production from the anterior pituitary gland, leading to excess cortisol release from the adrenal glands.
Often caused by a pituitary adenoma, it may also result from the excess production of corticotropin-releasing hormone (CRH) from the hypothalamus.
Cushing’s syndrome refers to the signs and symptoms associated with prolonged exposure to high cortisol levels, resulting from endogenous (like Cushing’s disease) or exogenous (like long-term corticosteroid use) causes.
Aetiology
Endogenous Cushing’s Syndrome:
Pituitary Adenoma: A benign tumour in the pituitary that secretes excessive ACTH, leading to increased cortisol production (Cushing’s disease).
Adrenal Tumours: Tumours in the adrenal glands, directly producing excess cortisol.
Exogenous Cushing’s Syndrome:
Long-Term Corticosteroid Use: Common cause from prolonged medication use (e.g., prednisone) for conditions like asthma or rheumatoid arthritis.
Epidemiology
Cushing’s disease is rare, typically presenting in the third and fourth decades of life.
The annual incidence of benign adrenal adenoma causing Cushing’s disease is 0.6 per million.
Pathophysiology
ACTH Action: Stimulates the adrenal cortex to produce cortisol; excessive ACTH (from a pituitary adenoma or ectopic source) leads to adrenal gland overstimulation and excess cortisol.
Cortisol Excess: Has wide-ranging effects on metabolism, immune function, and cardiovascular health; chronic cortisol excess disrupts these systems, leading to Cushing’s syndrome symptoms.
Symptoms
Physical Changes:
Weight gain (moon face, buffalo hump)
Thinning arms and legs, purple striae, easy bruising
Muscle weakness, thin, fragile skin
Increased facial/body hair (hirsutism in women)
Metabolic Disturbances:
High blood sugar, high blood pressure, dyslipidemia
Other Symptoms:
Menstrual irregularities, decreased fertility and libido
Osteoporosis, impaired wound healing, infections
Depression, anxiety, and cognitive issues
Diagnosis
Clinical Suspicion: Based on symptoms and medical history (e.g., corticosteroid use).
