Mifepristones relative binding affinity at the progesterone receptor is more than twice that of progesterone, its relative binding affinity at the glucocorticoid receptor is more than three times that of dexamethasone and more than ten times that of cortisol. Its relative binding affinity at the androgen receptor is less than one-third that of testosterone, and it does not bind to the estrogen receptor or the mineralocorticoid receptor.Mifepristone as a regular contraceptive at 2 mg daily prevents ovulation (1 mg daily does not). A single preovulatory 10-mg dose of mifepristone delays ovulation by three to four days and is as effective an emergency contraceptive as a single 1.5-mg dose of the progestin levonorgestrel.In women, mifepristone at doses greater or equal to 1 mg/kg antagonizes the endometrial and myometrial effects of progesterone. In humans, an antiglucocorticoid effect of mifepristone is manifested at doses greater or equal to 4.5 mg/kg by a compensatory increase in ACTH and cortisol. In animals, a weak antiandrogenic effect is seen with prolonged administration of very high doses of 10 to 100 mg/kg.In medication abortion regimens, mifepristone blockade of progesterone receptors directly causes endometrial decidual degeneration, cervical softening and dilatation, release of endogenous prostaglandins, and an increase in the sensitivity of the myometrium to the contractile effects of prostaglandins.
Microvillus inclusion disease, previously known as Davidsons disease, congenital microvillus atrophy and, less specifically, microvillus atrophy (note: microvillus is often misspelled as microvillous), is a rare genetic disorder of the small intestine that is inherited in an autosomal recessive pattern. Presentation
It is characterized by chronic, intractable diarrhea in new-born infants, starting in the first few days of life. This results in metabolic acidosis and severe dehydration. Pregnancy and birth are usually normal. Pathophysiology
It is caused by a congenital villus atrophy, atrophy of apical microvilli and intracellular accumulation of apical enzymes and transporters in the epithelial cells of the small intestine. MVID is in ost cases caused by mutations in the MYO5B gene. A minority of cases involves mutations in the STX3 gene. Diagnosis
Prenatal screening in utero is currently offered by several medical centers since the gene(s) involved in the disease were recently discovered to be MYO5B; Diagnosis is typically made by biopsy of the small intestine. Biopsy
The appearance of microvillous inclusion disease on light microscopy is similar to celiac sprue; however, it usually lacks the intraepithelial lymphocytic infiltration characteristic of celiac sprue and stains positive for carcinoembryonic antigen (CEA). The definitive diagnosis is dependent on electron microscopy. Differential diagnosis
The differential diagnosis of chronic and intractable diarrhea is:
Intestinal epithelial dysplasia
Syndromatic diarrhea
Immunoinflammatory enteropathy

Prognosis
It is nearly always fatal unless, like short bowel syndrome patients, treated with parenteral nutrition or an intestinal transplant.