Cushing’s syndrome is an endocrine disorder in which there is excess cortisol in the blood even when the individual is a stress-free state. In this syndrome, the adrenal gland secretes excessive cortisol.
The cause may be primary or secondary defect.
- A primary defect such as adrenal tumors that uncontrolled produce and release cortisol independent of ACTH can cause cortisol hypersecretion
- A secondary defect such as ACT-secreting tumor of the pituitary gland or CRH-secreting tumor of the hypothalamus, can also result in cortisol hypersecretion
Cortisol hypersecretion resulting from CRH-secreting tumor is rather rare; ACTH-secreting tumor of the pituitary usually is responsible for most secondary hypersecretion of cortisol.
Cortisol hypersecretion that results from ACTH-secreting tumor of the pituitary is commonly called Cushing’s disease.
SYMPTOMS OF CUSHING’S SYNDROME
Whatever the cause, the prominent symptoms of this syndrome are traceable to the exaggerated effects of cortisol.
The abnormally high blood levels of cortisol tends to promote uncontrolled breakdown (catabolism) of proteins in bone, muscle, skin and other organs. Consequently, bone strength declines and can even result in osteoporosis (loss of bone mass), muscles weaken, (due to loss of muscle protein), and the protein-poor skin becomes thinned and easily bruised.
2. Hyperglycemia and protein shortage
This widespread mobilization of amino acids from body proteins provides a large pool of free amino acids for use as glucose precursors in the gluconeogenic pathway. The conversion of too many amino acids into glucose makes the body suffer a combined glucose excess (hyperglycemia) and protein lack.
The uncontrolled breakdown of proteins may generate such a large quantity of precursors for hepatic gluconeogenesis that blood sugar rises to levels seen in diabetes.
The resultant hyperglycemia (high blood glucose) and glucosuria (glucose in urine) mimic diabetes mellitus. Since the person suffering Cushing’s syndrome may exhibit some of the same symptoms as a person with diabetes, the condition is sometimes referred to as adrenal diabetes.
3. “Moon face” and “buffalo hump”
For reasons that are unclear, part of the extra glucose get deposited as body fat in locations characteristic for this disease mainly in the trunk, face, and back of the neck. The abnormal fat distribution in the face (descriptively called moon face) and the back of the neck (called buffalo hump) are classical features of Cushing’s syndrome.
The loss of the collagen framework of bones weakens the skeleton, so fractures may occur from little physical trauma.
Other effects are those that arise from excessive protein breakdown. Loss of muscle protein results in muscle weakness and fatigue.
The protein-lacking, thin skin of the abdomen is over-stretched by the excessive underlying fat deposits forming irregular linear streaks.
The weakening of blood vessel walls due to depletion of structural proteins increases the tendency to bruise and to form localized patches of subcutaneous bleeding.
Wounds heal poorly because the production of collagen, a major structural protein found in scar tissue, is inhibited.