Regulation of ABC transporters by sex steroids may explain differences in drug resistance between sexes.

Drug efficacy is dependent on the pharmacokinetics and pharmacodynamics of therapeutic agents. Tight junctions, detoxification enzymes, and drug transporters, due to their localization on epithelial barriers, modulate the absorption, distribution, and the elimination of a drug. The epithelial barriers which control the pharmacokinetic processes are sex steroid hormone targets, and in this way, sex hormones may also control the drug transport across these barriers.

Estrogen receptors alpha and beta in human testis: both isoforms are expressed.

Currently, clinical and experimental evidence point to an essential role of estrogens and estrogen receptors in male fertility. The expression of estrogen receptor alpha (ERalpha) and beta (ERbeta) in human testis has been described. However, some studies were unable to detect ERalpha, while others report the expression of both isoforms, with ERbeta presenting a wide distribution within somatic and germinal testicular cells.