The main factors responsible for changes in the responsiveness of cell
s to steroid hormones observed in the course of neoplasia and ageing h
ave been analyzed. The decreased responsiveness is frequently reversib
le and appears to be unrelated to disturbances of the receptor apparat
us. The concept of multifunctional regulation of cell responsiveness t
o steroid hormones is advanced. Regulation is thought to involve two l
evels: receptor-mediated (signal transduction) and receptor-independen
t (changes in the activity of intracellular enzyme systems controlled
by the hormones). The role of microenvironment in the development of t
arget cell responses to steroid hormones is also discussed.