What do Adrenal Glands Do?Adrenal glands produce hormones required for healthy life. The adrenal cortex produces hormones that controls sex (androgens, estrogens), salt ballance in the blood (aldosterone), sugar ballance (cortisol). The adrenal medulla produces hormones involved in the fight or flight response (epinephrine and norepinephrine; adrenaline).
The Adrenal Medulla and Cortex Produce Very Different Hormones. We all have two adrenal glands located on the top of both kidneys. They are triangular shaped and measure about one-half inch in height and 3 inches in length. Each gland consists of a medulla (the center of the gland) which is surrounded by the cortex.
Function of the Adrenal Medulla.The adenal medulla is responsible for producing epinephrine and norepinephrine (adrenaline). We have all experienced that sudden "panic" feeling and anxiety when something happens suddenly and unexpectedly and we get scared. All of a sudden we have tingles and we feel like we need to run away or stand up and fight. This is the "flight or fight" symptoms and it is caused by the sudden release of adrenaline from our adrenal glands. (yes, adrenaline is called this because it comes from the adrenal gland). Adrenaline as we call it generically when talking to each other when we get scared can be broken down into two different hormones that the adrenal medulla produces: epinephrine and norepinepherine.
Function of the Adrenal Cortex.The adrenal cortex produces a handful of hormones necessary for fluid and electrolyte (salt) balance in the body such as cortisone and aldosterone. The adrenal cortex also makes sex hormones but this only becomes important if overproduction is present (most sex hormones are produced by the testes and ovaries).
- The Zona Glomerulosa. The most superficial layer of the adrenal cortex is the zona golmerulosa which produces the hormone aldosterone as well as some small amounts of progesterone (a sex hormone). The mineralocorticoid aldosterone is produced in the outermost layer of the adrenal cortex, the zona glo¬merulosa.
- The zona fasciculata is the middle zone of the adrenal cortex. The zona fasiculata primarily produces cortisol.
- The zona reticularis is the inner most zone of the adrenal cortex and it is adjacent to the inner adrenal gland called the adrenal medulla. Functions of the zona retularis is to store cholesterol for steroidogenesis (the making of steroids) and the secretion of sex hormones such as estrogen, and testosterone (in small amounts).
Technical Information for Doctors and Nurses.
In the zona glomerulosa (ZG), progesterone (a sex hormone) is converted through several steps to the mineralocorticoid aldosterone. In the other layers of the cortex, progesterone is converted first to 17-hydroxyprogesterone and then to either the 17-hydroxysteroid cortisol or the 17-ketosteroid sex hormones. Each day the adrenal glands secrete 15–20 mg of cortisol, 25–30 mg of androgens, and 75–125 µg of aldosterone.
The mineralocorticoid aldosterone is produced in the outermost layer of the adrenal cortex, the zona glo¬merulosa. Aldosterone secretion is primarily controlled through a renal pathway. Decreased arterial pressure or decreased serum sodium concentration is sensed by the juxtaglomerular apparatus and the macula densa, respec¬tively. The result is production and release of renin, activating angiotensin I. Within the lung, angiotensin-converting enzyme (ACE) converts most of the angiotensin I to the angiotensin II. Circulating angiotensin II stimulates aldosterone secretion. To a lesser degree, aldosterone secretion is stimulated by direct effects of ACTH and elevated serum potassium. With aging, there is decreased production of aldosterone.
The zona fasciculata (ZF) and zona reticularis (ZR) are responsible for glucocorticoid production. Secretion of cortisol is controlled via the hypothalamic-pituitary-adrenal (HPA) axis. Hypothalamic corticotropin-releasing hormone (CRH) causes release of adrenocorticotrophic hormone (ACTH) from the anterior pituitary gland, which stimulates the adrenal cortex to release cortisol. As cor¬tisol concentration achieves the physiologic range of 15–20 µg/dl, it exerts a negative feedback on both hypothal¬amus and anterior pituitary secretion. ACTH has a plasma half-life of 25 minutes and cortisol has a plasma half-life of 90 minutes. ACTH and cortisol production are constant over life in normal, unstressed individuals. Adrenal androgen release is regulated by ACTH, whereas gonadal release of testosterone and estrogen are under a separate pathway of pituitary gonadotrophic control. Androgen production peaks at puberty and progressively declines with advancing age.
Stimulation of the adrenal medulla is via preganglionic sympathetic fibers causing release of dopamine, norepinephrine, and epinephrine. Sympathetic neural outflow is increased by the fight-or-flight response, fear, emotional stress, upright posture, pain, cold, hypotension, hypoglycemia, and other stress. Norepinephrine exerts negative feedback at the preganglionic sympathetic receptors. With increasing age, there is no change in epinephrine levels, but norepinephrine and total plasma catecholamine are increased.
FIGURE 3: The capsule of the adrenal gland under microscope magnification, as well as the three layers, zona glomerulosa (ZG), zona fasciculata (ZF) and zona reticularis (ZR) of the adrenal cortex, responsible for producing adrenal cortex hormones.
Read more about the Mini Posterior Retroperitoneal Scope Adrenalectomy (Mini-PRSA). This is the preferred adrenal operation for about 95% of people with an adrenal tumor.