Recent epidemiological studies show that postmenopausal women taking estrogen-progestin hormone replacement therapy (HRT) have a higher risk of breast cancer than women on an HRT regimen lacking progestins. This may be related to the observation that progestin-treated breast cancer cells express and secrete high levels of vascular endothelial growth factor (VEGF), a potent angiogenic factor tha...

Progesterone influences most processes involved in female reproduction, including ovulation, sexual behaviour, pregnancy, parturition, lactation and maternal behaviour. One neurotransmitter through which progesterone might regulate many of these functions is dopamine. To determine where in the brain progesterone might alter dopaminergic activity necessary for these and other processes in rats v...

BACKGROUND Because unopposed estrogen substantially increases endometrial carcinoma risk, estrogen plus progestin is one menopausal hormone therapy formulation for women who have not had a hysterectomy. However, endometrial carcinoma risks among estrogen plus progestin users and among former unopposed estrogen users are not firmly established. METHODS We evaluated endometrial carcinoma risks ...

Ovarian cancer is the leading cause of reproductive cancer death in U.S. women. This high mortality rate is due to the lack of early detection methods and ineffectiveness of therapy for advanced disease. Until more effective screening methods and therapies are developed, chemoprevention strategies are warranted. The hen has a high spontaneous prevalence of ovarian cancer and has been used as a ...

The human progesterone receptor (PR) is expressed as two isoforms, PRA and PRB, which differ in the N-terminal region and exhibit different activities in vitro, with PRA demonstrating dominant negative inhibitory effects on the activity of PRB and other nuclear receptors. PRA and PRB are expressed in target tissues at comparable levels although cells expressing a predominance of one isoform can...

Progestin withdrawal is a crucial event for the onset of labor in many mammalian species. However, in humans the mechanism of a functional progestin withdrawal is unclear, because progestin concentrations do not drop in maternal plasma preceding labor. We report the presence of two novel functional membrane progestin receptors (mPRs), mPRalpha and mPRbeta, in human myometrium that are different...

CONTEXT The Women's Health Initiative trial of combined estrogen plus progestin was stopped early when overall health risks, including invasive breast cancer, exceeded benefits. Outstanding issues not previously addressed include characteristics of breast cancers observed among women using hormones and whether diagnosis may be influenced by hormone effects on mammography. OBJECTIVE To determi...

Norethindrone was the first progestin, a synthetic version of a natural steroid hormone, progesterone. A few birth control pills contain only a progestin, while the rest combine a progestin and an estrogen analogue. In the more than 60 years since Djerassi’s landmark synthesis, drug makers have experimented with different formulations of oral contraceptives, including introducing new types of p...

FKBP51 and FKBP52 are large molecular weight FK506-binding immunophilins that have diverse biochemical functions. Best studied is the role that they play as components of steroid hormone receptors. Differential display and gene array screens have identified FKBP51 as a progestin-inducible gene. Here we demonstrate progestin enhancement of FKBP51 mRNA and protein in T-47D cells. FKBP51 mRNA and ...

Recent clinical trials indicate that synthetic progestins may stimulate progression of breast cancer in postmenopausal women, a result that is consistent with studies in chemically-induced breast cancer models in rodents. However, progestin-dependent progression of breast cancer tumor xenografts has not been shown. This study shows that xenografts obtained from BT-474 and T47-D human breast can...