Abstract: Objective: To investigate the forming regularity and pathogenesis of DES induced pituitary prolactinoma and the preventing effects of anisodamine and progesterone. Methods: Ovariectomized female Wistar rats were randomly divided into 4 groups: (1) Control group (n=10): A blank implant was subcutaneously implanted over the neck; (2) Anisodamine group (n=10): An implant contained 10 mg anisodamine and an implant with 20 mg DES were subcutaneously coimplanted; (3) Progesterone group (n=10); 10 mg progesterone implant and 20 mg DES implant were co-implanted; (4) DES group (n=25): 20 mg DES implant only. Five rats in DES group were executed in Week 2、 4、 6、 8 and 10 respectively, and 5 rats in the remaining 3 groups were executed in week 8 and 10 respectively. Trunk blood sample were collected for serum PRL measurement. The anterior pituitary gland and hypothalamus were extirpated for PRL immunocytochemical examination and dopamine (DA) and norepinephrine (NE) measurement. Results: The weight of pituitary gland and serum and pituitary PRL levels in rats of the DES group were significantly greater than those of control group (all P＜0.01 or ＜0 05). Pituitary gland during week 2 and 4 presented lactotropic hyperplasia, and partial pituitary gland became prolactinoma in week 6, and all of them developed prolactinoma in week 8 and 10. The DA and NE concentrations in hypothalamus decreased to the nadir in week 4 and were significantly lower than those of control group (all P＜0.01). All the parameters mentioned above in anisodamine group and progesterone group were not signifiantly different to DES group (all P ＞0 05). Conclusion: (1) Subcutaneous DES implantation is capable of stimulating the lactotrope hyperplasia and finally forming prolactinoma in Wistar rat; (2) The decrease of hypothalamic DAand NE concentrations in DES group suggestes that hypothalamic dopaminergic and noradrenergic neurons take part in the regulation of PRL secretion; (3) The effect of progesterone protecting lactotropes against DES induced prolactinoma was not found; and (4) For no effect of amisodamine on preventing DES induced pituitary prolactinoma, the hypothalamic cholinergic neurons seem not to joint the regulation of pituitary PRL secretion.