The glycoprotein hormone family represents a class of heterodimers, that includes the placental hormone equine chorionic gonadotropin (eCG) and the anterior pituitary hormones‐ follitropin (FSH), lutropin (LH), and thyrotropin (TSH). The 4 hormones are heterodimers, with a common α‐subunit and unique β‐subunits. eCG is the most heavily glycosylated of the known pituitary and placental glycoprotein hormones. Recent observations using single chain glycoprotein hormone analogs in which, the β‐and α‐subunits are linked, implied that heterodimeric‐like quaternary configuration is not a prerequisite for receptor/signal transduction. To study the function and signal transduction of tethered rec‐eCG, a single chain eCG molecule was constructed and rec‐eCG protein was produced. Molecular mass of the single chain is about 45 kDa. All mice were ovulated by tethered rec‐eCG treatment. The dual activity of tethered rec‐eCG was determined in receptor cell lines of nonequid species; in fact, this dual activity was proven in species other than horse. Tethered rec‐eCG in equids does not bind to FSH receptors, suggesting that eCG is primarily an LH‐like hormone in the horse. Taken together, these data suggest that tethered rec‐eCG has dual activity in nonequid species in vitro. However, it has only LH‐like activity in equid species in vitro.