This study is the first attempt to examine the effects of NETA on immune cells and telocytes. The
results of this study form an important knowledge base for the development of new information
on the mechanism of contraceptive action of NETA in the uterus. Norethisterone acetate (NETA) is
a synthetic progestogen medication commonly utilized in birth control pills, menopausal hormone
therapy, and for curing abnormal uterine bleeding and endometriosis. Furthermore NETA has many
beneficial uses in veterinary medicine as control and synchronization of estrous cycle. The impact
of NETA on the endometrial stromal cells (ESCs), telocytes, and uterine immune cells is not well
understood. Therefore, this study focuses on assessing changes in uterine immune cells, ESCs, and
telocytes following exposure to NETA in albino rats. To achieve this objective, fourteen adult female
albino rats were randomly divided into two groups: a control group and an NETA-treated group. Rats
in the control group received daily pelleted food, water, and were oral administered of 2 ml distilled
water. In contrast, rats in the NETA-treated group received daily pelleted food, water, and were
orally administered 20 μg of NETA dissolved in 2 ml distilled water. The experiment spanned three
weeks. The findings of this study revealed that NETA usage increases the infiltration and activity of
immune cells (eosinophils, neutrophils, macrophages, lymphocytes, and mast cells). Furthermore,
it enhances the vesicular activity of uterine telocytes and their communication with various immune
cells. NETA also influences decidualization and the immunoexpression of progesterone receptors in
uterine epithelial and immune cells. This study concludes that the primary mechanism by which NETA
controls pregnancy is through decidual (pregnancy-like) effects or improper decidualization, which
inhibits fertilization and implantation respectively. Our research provides evidence of the contraceptive
mechanism of NETA from an immunological perspective in an animal model.