Effect of Particle Size on the Bioaccessibility of Progesterone from LoxOral in an In Vitro Dynamic Gastrointestinal System

Introduction: Hormonal replacement therapy (HRT) has been used extensively to treat the symptoms caused by decreased estrogen production following menopause, which can include vasomotor symptoms, urogenital atrophy, and mood or sleep disturbances (Ryan & Rosner, 2001). Estrogen therapy is frequently used in HRT and its pro-proliferative effects on the endometrium are counterbalanced by the use of progesterone, which is known to modulate the growthstimulatory effects of estrogen (Yang et al., 2011). Results from the Postmenopausal Estrogen/Progestin Interventions (PEPI) trial recommend that oral micronized progesterone be the first choice for estradiol opposing therapy in postmenopausal women (Miller et al., 1995; Barret-Connor et al., 1997).