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The biosynthesis of steroid hormones is a fascinating process . In this reaction cascade, cholesterol, a normal constituent of the lipid membrane bylayers, is coverted through a number of hydroylation, oxidation and reduction steps into a variety of biologically active substances, such as mineralocorticoids, glucocorticoids and sex hormones. Most of these modifications take place in the adrenal glands, testes and ovaries, although other tissues such as liver, kidney, placenta, brain, and skin are also quite active. The effect of steroid hormones is a complex, not yet fully understood process in which steroid hormones bind to specific intracellular receptors in the target cells, so that interactions with DNA in the nucleus are possible. What follows is a modulation of gene activity and a hormone- specific reaction occurs (1). Physiologically, sex hormones are important in every stage of life, from determining the sex differentiation, to the phenotypic differentiation in a female or male individual. They are also essential for a successful reproductive life and are involved in the development of the brain and the expression of gender specific behavior. Anomalies in each step of steroid hormone action have potential clinical consequences. Abnormalities in the receptor or post-receptor machinery lead to disturbances of the effect of a particular hormone. However, abnormalities of steroid hormone production can also lead to serious and complex effects. For example,the consequences of a block in the steroid synthesis ate twp-fold: on the one hand the lack of products has dramatic consequences in the development and function of the target organs; on the other hand the accumulation of the hormone upstream the block will cause the activation of other members of the steroid hormone receptor family. Both conditions can cause complex clinical pictures.