The third class of nuclear receptors (Nuclear, Class 3, Estrogen Receptor-like) includes estrogen and estrogen-related receptors (ER), as well as the 3-ketosteroid receptors (progesterone (PR), androgen (AR), gluco- and mineralocorticoid (GR and MR, respectively) receptors).
Androgens ((dihydro-) and testosterone) are the male sex hormones that belong to the steroid hormone family. They are mainly produced in testes, ovaries and adrenals. In early life, testicular androgens induce differentiation processes that lead to the development of the male phenotype. During adulthood, androgens remain essential for the maintenance of the male reproductive function, as well as a number of gender-dependent parameters like bone and muscle mass, hair growth and behavior. The androgen receptor (AR), holds a specific position within the group of steroid receptors, since several selective androgen response elements (selAREs) have been described that are not recognized by the other 3-ketosteroid receptors[1].