Cushing’s disease is caused by an adenoma of the pituitary gland, which causes an excessive production of cortisol by the adrenal glands. It is a very rare disease affecting about one to three in a million people a year. In children, Cushing’s disease affects more boys, but in adults in their forties more women are affected.
Causes of Cushing’s disease
The secretion of cortisol is normally controlled by another hormone, ACTH (Adrenocorticotropic hormone), which is produced by the pituitary gland, an endocrine gland at the base of the brain. When an adenoma (benign tumor) develops in the pituitary gland, the secreting cells multiply, leading to an overproduction of ACTH, which in turn stimulates the adrenal glands to produce cortisol. Cushing’s disease has no identified cause, either genetic or environmental.
NB: Although Cushing’s disease and Cushing’s syndrome both have similar symptoms their causes are different.
It should be noted that there are other endogenous causes of Cushing’s syndrome, but strictly speaking these are not the same as Cushing’s disease:
- Tumors in organs outside the pituitary gland that begin to secrete ACTH
- A tumor in the adrenal gland that secretes excess cortisol
Cushing’s syndrome can also have exogenous causes, through prolonged administration of high doses of synthetic corticosteroids.
Symptoms of Cushing’s disease
The most characteristic signs of Cushing’s disease are weight gain and changes in physical appearance due to prolonged exposure to cortisol. Patients with Cushing’s disease tend to have excess fat on the upper body, sometimes with a bump on the upper back (buffalo hump), a swollen and rounded face and thinner arms and legs. Other signs include the following:
- Muscular atrophy resulting in a lack of tone
- Thinning of the skin, with the appearance of bruising and difficulty in healing
- Purplish stretch marks, similar to stretch marks on the stomach and chest
Long term effects :
- High blood pressure
- Osteoporosis with risk of fatigue fracture;
- Reduced resistance to infection;
- Increased risk of diabetes
- Increased risk of kidney stones
- Mental disorders (depression, irritability, sleep disorders and even hallucinations).
Children with Cushing’s syndrome have stunted growth and stay short. In some people, the adrenal glands also produce large amounts of male sex hormones, which leads to excessive hair growth on the face and body, and in women to baldness.
Treatment of Cushing’s disease
Cushing’s disease can be cured by removing the pituitary adenoma that is responsible for the hypersecretion of ACTH. It is a delicate but not very traumatic operation in which an endoscope is inserted into the nasal cavity up to the pituitary gland. If the adenoma is well located, pituitary surgery allows complete remission in 70 to 80% of cases. The patient then looks normal again in a few months. The result is worse if the adenoma is too small to be found or if it is too large. In case of a relapse, a new intervention or radiotherapy can be considered.
After the operation, medical follow-up is necessary, as the removal of the pituitary gland sometimes leads to abnormally low concentrations of cortisol, thyroid and sex hormones, and ADH (antidiuretic hormone). The latter induces diabetes insipidus, which is characterized by constant thirst and frequent urination.