Aldosterone is the main hormone produced by the outer layer of the adrenal gland. Aldosterone is responsible for making your kidneys hold onto salt and water. However, despite aldosterone promoting salt and water retention by the kidneys, marked fluid retention is not usually observed in patients with aldosterone excess. Aldosterone also affects blood potassium levels by affecting urinary potassium loss. Thus, aldosterone excess (hyperaldosteronism) results in high blood pressure and low potassium levels in the blood.
Who should be screened for hyperaldosteronism?
Hyperaldosteronism was first described in 1955 by JW Conn in a patient with an aldosterone-producing adrenal tumor, whose high blood pressure improved after surgery in which the tumor was removed. At that time Dr. Conn felt that the prevalence of this condition could be as high as 20% in the hypertensive population spurring extensive research into this potentially curable form of hypertension. This condition now carries his name (Conn's syndrome). Current estimates on the prevalence of this condition vary, but we know that it is actually quite common in those patients requiring more than three blood pressure medications. Hyperaldosteronism related to a benign adrenal tumor occurs between two to three times more commonly in women and the peak incidence is between 30-50 years of age. There are no specific physical findings although patients with very low blood potassium levels may develop fatigue, muscle weakness, cramping, headaches and palpitations. Patients with hypertension can also developed a stroke, heart attack, abnormal heart rhythms and an enlarged heart.
The presence of a low blood potassium level in a patient with high blood pressure should always raise the possibility of hyperaldosteronism due to an adrenal tumor. A simple blood test can determine whether hyperaldosteronism is a potential cause of the high blood pressure. Imaging studies are helpful to document the presence of an adrenal tumor and either a CT scan or MRI are equally sensitive. If there is still uncertainty after these studies, a bilateral adrenal vein catheterization is used to localize the adrenal gland producing the elevated high aldosterone. Blood from both adrenal glands are sampled and compared. This is successful in up to 90% of patients.
In patients with adrenal tumors, surgery is the preferred treatment if the patient has difficult to control high blood pressure or persistent low blood potassium levels.
Removal of the adrenal tumor improves low blood potassium in all patients, and eliminates the need for blood pressure medication in 60-70% of patients. The outcomes are seen in patients who are less than 40 years old, have a tumor in one adrenal gland that is greater than 1-cm and have a normal second gland. Patients who tend to be less responsive to surgery and may have persistent high blood pressure after surgery are those who are older (>45 years), have a family history of hypertension, have hypertension for a long period of time and who did not respond the spironolactone. All patients however, have improvement in their blood pressure control, requiring fewer medications to control their blood pressure.
Laparoscopic adrenalectomy is currently the preferred technique used for removing the adrenal gland and is offered through the Adrenal Center at Georgia Regents Medical Center.