Estrogen receptor and estrogen metabolism pathway (ER/EM pathway)

The estrogen receptor and estrogen metabolism pathway encompasses the signaling mechanisms mediated by nuclear receptors (ER-alpha and ER-beta) and the enzymatic processes governing the synthesis and degradation of estrogens. Estrogens are critical steroid hormones that regulate diverse physiological processes, including reproductive development, bone density, and cardiovascular health. In many cancers, particularly breast and endometrial cancer, abnormal estrogen signaling or elevated local estrogen production drives tumor cell proliferation. The pathway also includes the G protein-coupled estrogen receptor (GPER1), which mediates rapid non-genomic effects. Therapeutic strategies targeting this pathway include selective estrogen receptor modulators (SERMs) like tamoxifen, selective estrogen receptor degraders (SERDs) like fulvestrant, and aromatase inhibitors (AIs) like letrozole, which block the conversion of androgens to estrogens. While highly effective in treating hormone-sensitive conditions, these interventions can lead to side effects such as bone loss, thromboembolic events, and menopausal symptoms.

Other names

Estrogen signaling pathwayEstrogen receptor signalingEstrogen metabolic pathwayEstrogen biosynthesis and actionER signaling

Drugs targeting this pathway primarily function by modulating the activity of estrogen receptors or by inhibiting the enzymes responsible for estrogen biosynthesis. Selective estrogen receptor modulators (SERMs) and degraders (SERDs) act as competitive antagonists or promote receptor degradation to block signaling in target tissues like the breast. Aromatase inhibitors (AIs) prevent the conversion of androgens into estrogens, thereby reducing systemic and local estrogen levels. Additionally, exogenous estrogens are used in hormone replacement therapy to activate these receptors in cases of deficiency.