This invention relates to oxysteroids and oxysteroid hormones which have been identified. These oxysteroids are C27 modified sterols, particularly derivatives of intermediates in 
cholesterol synthesis, including 
lanosterol, zymosterol and desmosterol, including C27 
diol and C27 acid derivatives, as well as related compounds and analogs thereof. The oxysteroids are capable of binding to or otherwise interacting with 
orphan nuclear receptors to result in modulation of 
gene expression. The invention further relates to methods of modulating the rate of 
cholesterol synthesis in a 
mammal. More specifically, the invention relates to treatment of 
cholesterol-related conditions which are improved or ameliorated by modulating the rate of 
cholesterol synthesis or 
cholesterol metabolism in a human in need thereof by administration of these oxysteroids, analogs or antagonists thereof. The invention includes methods for ameliorating, treating or preventing 
macular degeneration in a 
mammal comprising administering to said 
mammal an agent which stimulates or enhances the expression or activity of 
steroid sulphotransferase (SLUT2), particularly SLUT2B1b, or which stimulates or enhances the expression or activity of CYP27A1 or 
sterol 27-hydroxylase or otherwise increasing the sulfonation or 27-
hydroxylation of cholesterol intermediates, including 7-ketocholesterol. Assays for identification of analogs, antagonists or modulators of these oxysteroids or of 
sterol 27-hydroxylase are also provided.