Tertiary adrenal cortex insufficiency | Addison’s disease

Tertiary adrenal cortex insufficiency

Also the external supply of cortisol, such as in the form of tablets for the treatment of various diseases, can cause adrenal cortex insufficiency. Occasionally, this is also referred to as tertiary adrenal insufficiency. The pituitary gland shuts down its production of ACTH due to the increased amount of externally supplied cortisol. The adrenal gland reacts by stopping its production of cortisol due to the lack of a stimulating effect of the messenger substance ACTH on the adrenal gland.

Anatomy

The adrenal gland consists of two functionally different parts. The adrenal cortex produces hormones and the adrenal medulla produces catecholamines (adrenaline and noradrenaline). In Addison’s disease, only the cortex is affected.

Histologically, three layers can be seen in the adrenal cortex. The outer layer is called zona glomerulosa. It is responsible for the production of mineral corticoids (e.g. aldosterone).

The middle layer is the zona fasciculata and forms glucocorticoids (e.g. cortisol). In the innermost layer, the zona reticularis, mainly the male sex hormones androgens are produced. The adrenal glands are functionally independent of the kidneys. They are located at the upper pole of the kidneys, practically sitting on them. You can find out more about the structure and function of the adrenal glands in our topic: Adrenal gland.

Physiology

  • Mineralocorticoids
  • Glucocorticoids
  • Androgens

Mineralocorticoids belong to the class of steroid hormones. Their task is to regulate the electrolyte and water balance. The best known representative is aldosterone, which is produced from cholesterol.

It is also called thirst hormone. After its release from the zona glomerulosa of the adrenal cortex, it reaches the kidney, where it causes the sodium reabsorption of the filtered primary urine in the tubule system. At the same time, it ensures potassium and proton secretion.

Since chloride and osmotic water are reabsorbed in addition to sodium, it causes an increase in blood volume and thus blood pressure. Finally, it is also responsible for the reabsorption of sodium and water in the gastrointestinal tract. The effect takes place via the so-called renin-angiotensin-aldosterone system (RAAS).

Release impulses are changes in blood pressure and osmolarity (changes in the electrolytes in the blood). The glucocorticoids formed in the zona fasciculata (and partly also in the zona reticularis) also belong to the steroid hormones. Their task is to provide energy in stressful situations.

The most prominent representative is cortisol, which is transported in the blood mainly bound to proteins (transcortin and albumin). Androgens are sex hormones and cause, among other things, the development of secondary sexual characteristics. In men, androgens are mainly produced in the testicles.

Therefore, the loss of androgen production in men in Addison’s disease has little or no effect. Women are therefore mainly affected. In women, the androgens are the precursor of the estrogens (female sex hormones).