Background:Ghrelin, an endogenous ligand for the growthsecretagogue receptor is predominantly produced in the stomach and anexpression of ghrelin has recently been identified in placenta and ovary. OBJECTIVES: Therefore, we decited to measure ovarian ghrelin as quantitative andevaluate the correlation between ghrelin and estrogen during second half ofovine pregnancy. METHODS: The ovarian samples were collected from 40pregnant sheep in 3, 3.5, 4, 4.5 and 5 months of pregnancy in a local abattoir.Follicles and active corpora lutea (CL) were dissected from surroundingtissues, separately. The samples were homogenized with phosphate buffer (0.1 M,pH=7.4) on liquid nitrogen to provide fluid samples. Ghrelin and estrogenconcentrations were measured by ELISA method and expressed as milligram (mg)and picogram (pg) per mg of tissue protein, respectively. RESULTS:There was a linear correlation between ghrelin and estrogen in ovarian follicles(r=0.97 and p=0.004), but not in CL. Follicular ghrelin significantly increasedin 4, 4.5 and 5 months (p<0.001) but CL ghrelin significantly decreased inthe 4.5 month of ovine pregnancy (p<0.01). Estrogen concentration was alsosignificantly higher in 4-5 months of pregnancy in ovarian follicles(p<0.001) but potent CL indicated higher estrogen level only in the 5thmonth of pregnancy (p<0.001). CONCLUSIONS:These results emphasize the role of ghrelin inthe reproductive system and open a new window to future studies