ABSTRACT
Sex determination followed by sex differentiation is an orderly sequence of events coordinated in a time-and thresholddependent manner via a network involving numerous genes and hormones, particularly sex steroids. Understanding this process is a prerequisite to the investigation of a newborn infant with ambiguous genitalia. Indeed, much of the current knowledge about the genetic control of sex determination has been gleaned from studying individuals with syndromes of sex reversal, such as complete XY gonadal dysgenesis and the XX male. Similarly, the study of individuals with defects in steroid biosynthesis or action has provided information about novel pathways of steroid production and the mode of action of hormones at target sites.
