In the two decades since the discovery of the steroid hormone receptors, a great deal has been learned about their structure, their relationships with each other, and the target sequences (response elements) at which they regulate expression of specific genes. Analysis of receptor sequences has confirmed the existence of several domains with distinct functions in each receptor molecule, and has also indicated that the steroid receptors are members of a 'superfamily' which also includes receptors for vitamin D, retinoic acid, thyroid hormone and its related oncogene v-erbA, and a substantial number of 'receptors' whose ligands are still unidentified. The response element sequences are also closely related, and we are beginning to understand the interaction of the receptors with these response elements and with proteins bound nearby such as transcription factors. Certain naturally occurring genetic diseases have been identified with specific receptor mutations. The future promises greater understanding not only of the detailed action of the receptors of this superfamily, but of their precise role in fertility, development, and disease.
