Trans-Clomiphene citrate is the citrate salt of the trans-isomer of clomiphene. It is a non-steroidal selective estrogen receptor modulator (SERM) with a triphenylethylene core structure. This specific isomer is a key component of the racemic mixture used in pharmaceutical formulations. Its primary and well-established application is as an active pharmaceutical ingredient (API) in fertility treatments. It is used to induce ovulation in women with ovulatory dysfunction, such as those with polycystic ovary syndrome (PCOS). The mechanism of action involves competitive antagonism of estrogen receptors at the hypothalamus, which disrupts the normal negative feedback loop, leading to increased secretion of gonadotropin-releasing hormone (GnRH), follicle-stimulating hormone (FSH), and luteinizing hormone (LH), thereby stimulating ovarian follicular development. While primarily known for its use in female infertility, research has explored its off-label applications in male hypogonadism and for the management of certain endocrine conditions. It is a prescription drug subject to strict regulatory controls.