STEROIDAL DRUGS

STEROIDAL DRUGS

Steroids in general ate tetracyclic compounds characterized by the presence of a perhydro-1,2-cyclopentenophenanthrene ring system. The three cyclohexane rings are designated as A.B.C and the cyclopentane ring is the D-ring. These are colourless crystalline compounds and widely distributed in animals and plants. All the steroids give, among other products, Diel's hydrocarbon on dehydration with selenium at 360°C. They possess an alcoholic group; may be saturated (plant sterols) and unsaturated (animal and many plant sterols); they occur free or esters of the higher fatty acids. Mammalian endocrine glands have been the source of several hundred naturally occurring steroids, many with biochemical, clinical or therapeutic significance.

On the basis of their sources, sterols are classified as :

1. Zoosterol, which have been isolated from animals, e.g. cholesterol, cholestanol, coprostanol.

2. Phytosterol, which are obtained from plant sources, e.g. sitosterol, stigmasterol, and --

3. Mycosterol, which are obtained from yeast and fungi, e.g. ergosterol.

Androstane is the simple parent hydrocarbon containing 19 carbons. The male sex hormone testosterone is derived from androstane. The  oestrogenic hormone oestradiol is a derivative of estrane which possesses 18 carbons.

Steroidal drugs act as hormones. The hormones are the internal secretion of the endocrine (ductless) glands required for the specific physiological function(s). These are brought to th organ where required by blood streams.

The progestational hormone progesterone and adrenocortical hormones are the derivatives of pregnane.

Steroid sex hormones are produced in gonads, ovaries, testes, adrenal cortex and the placenta. They influence the development and maintenance of the reproductive organs. There are three main typés of sex hormones.

Androgens have distinct roles i nale sex physiology. The oestrogens and progesterone insistence the female sex physiology.

The adrenal cortex synthesizes three types of steroids  -the glucocorticoids, mineralocorticoids and sex corticoids (e.g. Oestrogens and androgens). The glucocorticoids, namely cortisone and hydrocortisone, have their action on gluconeogenesis, glycogen deposition and protein and calcium metabolism. The mineralocorticoids (e.g. deoxycortone and aldosterene) have their action on electrolyte and water metabolism causing sodium and fluid retention and potassium excretion.