Corpus Luteum Presence as a Risk Factor for Endometrial Hyperplasia in Clinically Healthy Female Cats Undergoing Routine Ovariohysterectomy

In this prospective cross-sectional study, we investigated whether corpus luteum (CL) presence is associated with subclinical endometrial hyperplasia in clinically healthy female cats undergoing elective ovariohysterectomy. Fifty intact female cats (13-27 months, ASA I) presented for routine surgery were enrolled. Following ovariohysterectomy, uteri and ovaries were subjected to full-thickness histopathological examination, and uterine lesions and ovarian structures, including CL and cysts, were systematically recorded. Descriptive statistics were used to determine the prevalence of uterine and ovarian findings, and the association between CL presence (as a proxy for luteal-phase progesterone exposure) and endometrial hyperplasia (EH) was evaluated using Fisher’s exact test with calculation of odds ratio (OR) and 95% confidence interval (CI). Despite the absence of reproductive complaints, EH and cystic endometrial hyperplasia (CEH) were identified in 36% (18/50) and 20% (10/50) of female cats, respectively, while mild endometritis and other hyperplastic lesions were detected in 12% and 8%. Ovarian cysts, predominantly follicular, were present in 34% of cats, and CLs were observed in 48% (24/50). Female cats with CL had a significantly higher prevalence of EH than those without CL (54.2% vs 19.2%; p=0.014), corresponding to an OR of 4.96 (95% CI 1.4-17.6), indicating that luteal-phase animals were nearly five times more likely to exhibit EH. These findings demonstrate that progesterone-associated endometrial changes are common and largely subclinical in young, clinically healthy female cats and support CL presence as a clinically relevant risk factor for early uterine remodeling, warranting further investigation into the long-term significance of these lesions.