The symptoms and treatment of all three are similar. Some doctors recommend a tilt table test to confirm these diagnoses, however I have not found tilt table testing to be that helpful.
The treatment for low aldosterone starts off by increasing salt intake. Patients can also take licorice or licorice root, or grapefruit or grapefruit juice, as these block the enzyme that breaks down cortisol in the kidneys and allows cortisol to bind to the aldosterone receptor in the kidneys and helps raise blood pressure.
For more severe cases I often give fludrocortisone which is also called Florinef. Florinef is a pretty benign medicine which is a mineralocorticoid unlike cortisol which is a glucocorticoid. These combinations of medicines which raise blood pressure usually help the patient's symptoms and gives more energy and less dizziness on standing.
A patient with high aldosterone and low renin could have an aldosterone secreting adrenal tumor. These patients often have high blood pressure and low potassium and patients suspected of having high aldosterone should have a potassium, aldosterone and renin level measured that can be done at any time a day in any position.
If low renin and high aldosterone is found, I usually order an adrenal CAT scan to look for tumors. If a tumor is found, I order other tests to make sure the aldosterone is truly high. I will then refer the patient for adrenal surgery.
The other important axis of water balance is controlled by the hormone, arginine vasopressin (AVP); it's also called antidiuretic hormone or ADH. This hormone is made by the posterior pituitary and regulates water retention in the kidney, causes blood vessels to constrict and acts, along with CRH, to secrete ACTH from the pituitary which goes to the adrenals to secrete cortisol.
Patients with pituitary problems especially in the posterior pituitary, often from surgery or prior radiation, could be deficient in ADH and have a condition called diabetes insipidus (DI).
Rarely the diabetes insipidus could be due to problems with the ADH receptor at the kidney.