[Endocrinology] The adrenal gland

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Physiology

The adrenal gland receives signals from the pituitary via adreno-cortico-tropic hormone (ACTH). The pituitary is signalled by corticotropin-releasing hormone from the hypothalamus. The hypothalmus is a part of the limbic system and hypothalmic output is modulated by many neural structures. 

This gateway between the brain and the adrenal gland is called the hypothalamic–pituitary–adrenal axis.

The adrenal gland produces several hormones which each have different effects. The general theme of adrenal gland activity is to prepare the body for flight or flight.

1. Epinephrine / norepinephrine can immediately increase the heart rate and stroke volume, increasing blood pressure and the rate of flow of oxygen and glucose around the circulatory system. These neurotransmitters also promote feelings of agitation and anxiety in the brain. 
2. Androgens (Testosterone) stimulate muscle and bone growth. They promote the development of sexual dimorphism during puberty. They also promote libido and sexual arousal. They are produced in both male and female bodies. 
3. Glucocorticoids (Cortisol) suppress protein synthesis and immune system activity. They promote the mobilisation of the building blocks of proteins (amino acids, glucose, etc.) into the blood stream. 
4. Mineralocorticoids (Aldosterone) act on the kidneys. They promote the retention of water and sodium ions in the blood stream. This raises the blood pressure. They also promote the excretion of potassium ions into the urine.

Hormones

• Stimulated by: Adrenocorticotropic hormone
• Output: Norepinephrine
• Output: Epinephrine
• Output: Testosterone
• Output: Cortisol
• Output: Aldosterone

 

Pathophysiology

Iatrogenic

• Cushing's syndrome (Hypercortisolism)

Adrenal hyperfunction

Causes

• Congenital adrenal hyperplasia  
• Adrenocortical adenoma
• Adrenocortical carcinoma
• Phaeochromocytoma 

Consequences

• Ectopic Cushing's syndrome (Hypercortisolism)
• Cushing's disease (Hypercortisolism)
• Primary aldosteronism (Conn's syndrome)

 

Adrenal hypofunction /Adrenal insufficiency

Causes

• Corticosteroid withdrawal
• Congenital adrenal hyperplasia 
• Infections
• Haemorrhage
• Waterhouse–Friderichsen syndrome
• Autoimmune diseases
• Adrenocortical carcinoma
• Amyloidosis

Consequences

• Addison's disease (Primary hypocortisolism)
• Addisonian crisis (Secondary hypocortisolism)  
• Hypoaldosteronism
• Acute adrenal insufficiency: Endocrine shock