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==Introduction==

==Introduction==

Steroids are 21-carbon, 4-ring molecules, with biologically active steroids have a double covalent bond between carbon atoms 4 and 5, and a ketone group at C3. The body endogenously produces steroids which are essential for life; they regulate a variety of functions under normal physiological conditions and have important roles in response to stress. These steroids are  produced in the [[Adrenal Glands - Anatomy & Physiology#Adrenal Glands|adrenal cortex]] and are therefore known as "corticosteroids". The corticosteroids can be further divided to [[Adrenal Glands - Anatomy & Physiology#Mineralocorticoids|mineralocorticoids]] and [[Adrenal Glands - Anatomy & Physiology#Glucocorticoids|glucocorticoids]] which are synthesised in different areas of the cortex. [[Adrenal Glands - Anatomy & Physiology#Mineralocorticoids|mineralocorticoids]] (such as aldosterone) are produced in the [[Adrenal Glands - Anatomy & Physiology#Adrenal Glands|zona glomerulosa]]; [[Adrenal Glands - Anatomy & Physiology#Glucocorticoids|glucocorticoids]] include cortisol (from the [[Adrenal Glands - Anatomy & Physiology#Adrenal Glands|zona fasiculata]]) and corticosterone (from the [[Adrenal Glands - Anatomy & Physiology#Adrenal Glands|zona reticularis]]). Corticosteroids are synthesised from plasma cholesterol which is stored in the adrenal gland and assimilated to corticosteroids as they are required. Endogenous glucocorticoid levels are regulated by the [[Adrenal Glands - Anatomy & Physiology#Glucocorticoids|hypothalamus-pituitary adrenal axis]], whereas the [[Renin Angiotensin Aldosterone System|renin angiotensin aldosterone system]] controls [[Adrenal Glands - Anatomy & Physiology#Mineralocorticoids|mineralocorticoid]] levels.

Steroids are a diverse class of molecules, all of which have a 21-carbon, 4-ring skeleton. Biologically active steroids have a double covalent bond between carbon atoms 4 and 5, and a ketone group at C3. The body endogenously produces steroids which are essential for life; they regulate a variety of functions under normal physiological conditions and have important roles in response to stress. These steroids are  produced in the [[Adrenal Glands - Anatomy & Physiology#Adrenal Glands|adrenal cortex]] and are therefore known as "corticosteroids". The corticosteroids can be further divided to [[Adrenal Glands - Anatomy & Physiology#Mineralocorticoids|mineralocorticoids]] and [[Adrenal Glands - Anatomy & Physiology#Glucocorticoids|glucocorticoids]] which are synthesised in different areas of the cortex. [[Adrenal Glands - Anatomy & Physiology#Mineralocorticoids|mineralocorticoids]] (such as aldosterone) are produced in the [[Adrenal Glands - Anatomy & Physiology#Adrenal Glands|zona glomerulosa]]; [[Adrenal Glands - Anatomy & Physiology#Glucocorticoids|glucocorticoids]] include cortisol (from the [[Adrenal Glands - Anatomy & Physiology#Adrenal Glands|zona fasiculata]]) and corticosterone (from the [[Adrenal Glands - Anatomy & Physiology#Adrenal Glands|zona reticularis]]). Corticosteroids are synthesised from plasma cholesterol which is stored in the adrenal gland and assimilated to corticosteroids as they are required. Endogenous glucocorticoid levels are regulated by the [[Adrenal Glands - Anatomy & Physiology#Glucocorticoids|hypothalamus-pituitary adrenal axis]], whereas the [[Renin Angiotensin Aldosterone System|renin angiotensin aldosterone system]] controls [[Adrenal Glands - Anatomy & Physiology#Mineralocorticoids|mineralocorticoid]] levels.

 

 

==Mechanism of Action==

==Mechanism of Action==

Suppression of the hypothalamus-pituitary axis can occur. Exogenous steroids extert negative feedback in the same way that endogenous steroids do. This leads to suppression of ACTH formation and storage and may cause atrophy of the pituitary gland. Sudden termination of treatment with exogenous steroids can therefore lead to failure of production of endogenous steroids, causing a crisis. This means that gradual dose reduction is of paramount importance. One method of achieving this is by alternate day thereapy, where a short-acting glucocorticoid in a short-acting formulation us used every other day at times to conincide with peak endogenous steroid levels.

Suppression of the hypothalamus-pituitary axis can occur. Exogenous steroids extert negative feedback in the same way that endogenous steroids do. This leads to suppression of ACTH formation and storage and may cause atrophy of the pituitary gland. Sudden termination of treatment with exogenous steroids can therefore lead to failure of production of endogenous steroids, causing a crisis. This means that gradual dose reduction is of paramount importance. One method of achieving this is by alternate day thereapy, where a short-acting glucocorticoid in a short-acting formulation us used every other day at times to conincide with peak endogenous steroid levels.

Another serious side effect of steroid administration is iatrogenic [[Canine Hyperadrenocorticism|Cushing's disease]] (hyperadrenocorticism). This can result from prolonged glucocorticoid treatement, and signs can include polydipsia, polyuria, polyphagia, elevation of liver enzyme levels and a pot-belly.

Another serious side effect of steroid administration is iatrogenic [[Hyperadrenocorticism|Cushing's disease]] (hyperadrenocorticism). This can result from prolonged glucocorticoid treatement, and signs can include polydipsia, polyuria, polyphagia, elevation of liver enzyme levels and a pot-belly.

==Drugs in This Group==

==Drugs in This Group==

Steroids can be used as treatment in a wide variety of clinical scenarios. For example, one major use of steroids is against inflammatory disease. Both acute inflammatory disease (such as allergic reactions) and chronic conditions (such as osteoarthritis) may benefit from the administration of steroids.

Steroids can be used as treatment in a wide variety of clinical scenarios. For example, one major use of steroids is against inflammatory disease. Both acute inflammatory disease (such as allergic reactions) and chronic conditions (such as osteoarthritis) may benefit from the administration of steroids.

Immune-mediated disorders can also be treated with steroids. Initially, high doses are used which are gradually decreased until an effective maintenance dose for that individual is reached. In protocols such as this, steroids may be used in conjunction with other immuno-supressive drugs. Examples of diseases that may be treated this way are [[Immune Mediated Haemolytic Anaemia|immune-mediated haemolytic anaemia]], [[Muscles Developmental - Pathology#Myasthenia gravis (MG)|myasthenia gravis]] and immune-mediated skin disease.

Immune-mediated disorders can also be treated with steroids. Initially, high doses are used which are gradually decreased until an effective maintenance dose for that individual is reached. In protocols such as this, steroids may be used in conjunction with other immuno-supressive drugs. Examples of diseases that may be treated this way are [[Immune Mediated Haemolytic Anaemia|immune-mediated haemolytic anaemia]], [[Myasthenia Gravis|myasthenia gravis]] and immune-mediated skin disease.

Steroids can be used to treat shock. The timing of treatment is important in this instance, and a high dose of a short-acting glucocorticoid is usually used.  Cerebral oedema can also be treated with steroids.

Steroids can be used to treat shock. The timing of treatment is important in this instance, and a high dose of a short-acting glucocorticoid is usually used.  Cerebral oedema can also be treated with steroids.