Antidiuretic hormone (ADH or vasopressin) controls water reabsorption in the nephron. When levels of fluid in the blood drop, the hypothalamus causes the pituitary to release ADH. This increases the permeability of the collecting ducts to water, allowing more water to be absorbed from the urine into the blood. The resulting urine is more concentrated. When there is too much fluid in the blood, sensors in the heart cause the hypothalamus to reduce the production of ADH in the pituitary, decreasing the amount of water reabsorbed in the kidney. This results in a lower blood volume and larger quantities of more dilute urine.
What do adrenal hormones do?
Cortisol belongs to a class of hormones called glucocorticoids, which affect almost every organ and tissue in the body. Cortisol's most important job is to help the body respond to stress. Among its many vital tasks, cortisol helps * maintain blood pressure and cardiovascular function * slow the immune system's inflammatory response * maintain levels of glucose-a form of sugar used for energy-in the blood * regulate the metabolism of proteins, carbohydrates, and fats
The amount of cortisol produced by the adrenals is precisely balanced. Like many other hormones, cortisol is regulated by the brain's hypothalamus and the pituitary gland. First, the hypothalamus releases a "trigger" hormone called corticotropin-releasing hormone (CRH) that signals the pituitary gland. The pituitary responds by sending out ACTH, which in turn stimulates the adrenal glands. The adrenal glands respond by producing cortisol. Completing the cycle, cortisol then signals back to both the pituitary and hypothalamus to decrease these trigger hormones.
The hypothalamus sends CRH to the pituitary, which responds by sending out ACTH. ACTH then causes the adrenals to release cortisol into the bloodstream.
Aldosterone belongs to a class of hormones called mineralocorticoids, also produced by the adrenal glands. Aldosterone helps maintain blood pressure and water and salt balance in the body by helping the kidneys retain sodium and excrete potassium. When aldosterone production falls too low, the kidneys are not able to regulate water and salt balance, leading to a drop in both blood volume and blood pressure.
What are the symptoms of adrenal insufficiency?
The symptoms of adrenal insufficiency usually begin gradually. The most common symptoms are * chronic, worsening fatigue * muscle weakness * loss of appetite * weight loss
Other symptoms can include * nausea * vomiting * diarrhea * low blood pressure that falls further when standing, causing dizziness or fainting * irritability and depression * a craving for salty foods due to salt loss * hypoglycemia, or low blood glucose * headache * sweating * in women, irregular or absent menstrual periods
Hyperpigmentation, or darkening of the skin, can occur in Addison's disease but not in secondary adrenal insufficiency. This darkening is most visible on scars; skin folds; pressure points such as the elbows, knees, knuckles, and toes; lips; and mucous membranes such as the lining of the cheek.
Because the symptoms progress slowly, they are often ignored until a stressful event like an illness or accident causes them to worsen. Sudden, severe worsening of symptoms is called an Addisonian crisis, or acute adrenal insufficiency. In…