Steroid sulfatase catalyzes desulfation of all 3ß-hydroxysteroid sulfates.  Steroid sulfates are water-soluble storage or excretory forms of active hormones.  Although cholesterol sulfate is the least soluble of the 3ß-hydroxysteroid sulfates, it can act as a detergent and can form a micelles or mixed micelle in aqueous solutions due to its amphibic nature.  The sulfated form of steroid hormones, which is inactive because of failure to bind to their receptors, becomes active after desulfation by STS.  X-linked ichthyosis is an inherited skin disease caused by a lack of steroid sulfatase enzyme activity. 

Accumulation of cholesterol sulfate in the epidermis accounts for the symptoms of this disease.  XLI is diagnosed by assaying STS activity in the placenta of the patient’s mother or in lymphocytes of the patient after birth.  The STS gene has been cloned, and it has been found that most XLI patients have total deletion of the STS gene.  Southern blotting using full-length STS cDNA as a probe is useful for diagnosis of XLI.  PCR using STS gene and ß-globin gene primers with high-performance liquid chromatography is also useful for screening for carriers of STS defects.