Cushing's disease, also referred to as Cushing's syndrome, occurs when the adrenal glands in your body produce too much of the steroid hormone cortisol. Doctors call cortisol the stress hormone because it regulates the changes that occur in response to stress, such as increasing blood sugar levels, balancing fluid levels and mobilizing nutrients. A study published in "The Endocrinology Journal" reports osteoporosis, a condition of weak bones caused by low calcium levels, as the main complication of Cushing's disease.
Cushing's Symptoms
The increase in cortisol causes a variety of symptoms. Many patients develop characteristic physical features like a moon face, a buffalo hump on the upper back or neck, thinning of the skin, frequent bruises, stretch marks on the abdomen, thighs or breasts, increased acne, facial hair growth and loss of scalp hair in women. Other symptoms include fatigue, weight gain, weakness, depression, mood swings and increased thirst. Cushing's disease causes potassium levels to drop, which contributes to high blood pressure, and calcium levels to decrease, leading to osteoporosis.
Bone Formation
Because bones are strong and hard many people forget that they consist of living tissue. Your bones undergo a continual process of breakdown and reformation. As bone tissue ages, your body breaks it down. It then uses minerals including calcium and phosphorus to build new bone tissue. During childhood and adolescence your body builds bone faster than it breaks it down. As you age, the production of new bone tissue slows down which leaves bones vulnerable to becoming weak and brittle. For this reason the Institute of Medicine recommends adults over the age of 50 increase their calcium intake to 1,200 mg per day.
Cushing's Effects
The increase in the steroid hormone cortisol affects the balance of calcium and phosphorus in your body, but researchers continue to study the exact mechanism of action involved. The minerals calcium and phosphorus get deposited to build new bone tissue but other minerals like magnesium play a role in maintaining mineral balance. In addition, your body can only absorb calcium in the presence of adequate levels of vitamin D. One study published in "The Journal of Clinical Endocrinology and Metabolism" found that patients with Cushing's disease have impaired absorption of calcium through the intestine but that the impairment does not involve vitamin D levels.
Types of Cushing's Disease
The adrenal glands, located above each kidney, produce cortisol. Tumors of the adrenal glands can cause the overproduction of cortisol. Doctors refer to this type of Cushing's disease as adrenal Cushing's disease. Cushing's disease can also occur when the pituitary gland, located at the base of the brain, produces too much adrenocorticotrophic hormone, known as ACTH, which signals the adrenal glands to produce cortisol. This type of Cushing's disease, known as pituitary Cushing's disease, accounts for approximately 70 percent of all cases of spontaneous Cushing's disease, as reported by The National Adrenal Diseases Foundation. A study published in "The Endocrinology Journal" found that osteoporosis is more prevalent, and therefore calcium levels lower, in patients with adrenal Cushing's disease.
References
- "The Endocrinology Journal"; Osteoporosis is More Prevalent in Adrenal Than in Pituitary Cushing's Syndrome; Ohmori, N. et al.; February 2003
- Lab Tests Online: Cushing's Syndrome; February 2009
- "Journal of Clinical Endocrinology and Metabolism"; Vitamin D Meatolites and Parathyroid Hormone in Cushing's Syndrome; Findling, J et al.; May 1982
- The National Adrenal Diseases Foundation: Cushing's Disease; Dr. Paul Margulies
- Institute of Medicine: Dietary Reference Intakes Summary; 2004
