Post natal oestrogen administration stimulates precocious endometrial gland development in the horse.

This study investigates the impact of synthetic progestagen and oestrogen on the development of endometrial glands in newborn female horses, aiming to suppress endometrial gland development to understand the role of these glands in embryogenesis and early fetal development.

Research Methods

• The study involved nine Thoroughbred filly foals separated into three groups.
• Group A received subcutaneous implants of the weakly active progestagen, norgestomet, from birth to age 6 months, along with fortnightly intramuscular injections of oestradiol valerate and norgestomet.
• Group B were given an oral highly active progestagen, altrenogest, daily from birth to age 6 months with fortnightly injections of oestradiol valerate and norgestomet.
• Group C acted as the control group and received no treatment.
• Endometrial biopsies were taken at age 6 months and 2 years to assess the endometrial gland development and to determine the presence or absence of oestrogen and progesterone receptors in the endometrial tissues.

Research Findings

• No endometrial gland development was observed in Groups B and C. Group A showed a high degree of endometrial gland development and positive staining for both oestrogen and progesterone receptors at age 6 months.
• All nine fillies showed full normal endometrial gland development at the age of 2 years.

Conclusion

• The study concluded that administration of a strongly active progestagen was able to suppress endometrial gland development during the treatment. However, treatment with oestradiol valerate together with a weakly active progestagen stimulated early endometrial gland development.
• Neither steroid was able to create the desired uterine gland knockout (UGKO) model, indicating these treatments failed to permanently suppress endometrial gland development.
• The study suggests that ovarian oestrogen, rather than progesterone, seems to be the basic stimulus for endometrial gland development in horses.
• As all the fillies showed normal endometrial gland development and fertility after puberty, this negated the initial hypothesis for creating a UGKO model to study the implications in embryogenesis and early fetal development.