I. Normal Adrenal Function
The adrenal glands are located above each kidney. Each adrenal gland is made up of two regions, the inner region (called the medulla) which produces adrenaline and the outer region (called the cortex) which produces adrenal steroid hormones. Three types of adrenal steroids are produced; glucocorticoids ("sugar hormones"), mineralocorticoids ("salt-water hormones") and androgens ("male hormones"). It is these hormones which are produced in abnormal amounts in people with CAH.
The normal production of adrenal hormones results from a multi-step chain of events that occurs between the brain and the adrenal glands. The pituitary gland located at the base of the brain produces the AdrenoCorticoTropic Hormone (ACTH) which activates the adrenal glands to produce cortisol. Cortisol and ACTH work "in balance" - when cortisol in the blood is too high, it "turns off" additional ACTH production, hence returning cortisol production to normal. In contrast, when cortisol in the blood is too low, ACTH production increases until cortisol concentrations return to normal.
It is important to remember that cortisol production doubles or triples at the time of medical, surgical or psychological stress.
Aldosterone (salt - water hormone) secretion is under the control of another hormone, angiotensin, which itself is under control of the hormone renin produced by the kidneys. When aldosterone is too low, salt (NaCl) levels in the blood fall as does total body water. This leads to an increase in renin, which then causes an increase in angiotensin production, and subsequently a return of aldosterone concentrations back to normal. When aldosterone is too high, serum sodium, total body water and blood pressure increase, resulting in decreased renin and angiotensin production until aldosterone returns to normal.
C. Adrenal Androgens
During fetal life prior to birth a large amount of adrenal androgen is secreted in both males and females. At 3-6 months after birth, secretion of adrenal androgen stops.
During puberty, adrenal androgen secretion resumes in both boys and girls. These androgens are responsible for the development of pubic and axillary hair in girls. In boys, the production of testicular androgens (which is about 10 times more active than adrenal androgens) play the major role in male masculinization.