5α-DHNET specifically has been assessed and found to be selective in its inhibition of aromatase, and does not affect cholesterol side-chain cleavage enzyme (P450scc), 17α-hydroxylase/17,20-lyase, 21-hydroxylase, or 11β-hydroxylase. Since it is not aromatized (and hence cannot be transformed into an estrogenic metabolite), unlike norethisterone, 5α-DHNET has been proposed as a potential therapeutic agent in the treatment of ER-positive breast cancer. Other activities
Norethisterone is a very weak inhibitor of CYP2C9 and CYP3A4 (IC50 = 46 μM and 51 μM, respectively), but these actions require very high concentrations of norethisterone that are far above therapeutic circulating levels (which are in the nanomolar range) and hence are probably not clinically relevant.Norethisterone and some of its 5α-reduced metabolites have been found to produce vasodilating effects in animals that are independent of sex steroid receptors and hence appear to be non-genomic in mechanism.Norethisterone stimulates the proliferation of MCF-7 breast cancer cells in vitro, an action that is independent of the classical PRs and is instead mediated via the progesterone receptor membrane component-1 (PGRMC1). Certain other progestins act similarly in this assay, whereas progesterone acts neutrally. It is unclear if these findings may explain the different risks of breast cancer observed with progesterone and progestins in clinical studies. Antigonadotropic effects
Due to its progestogenic activity, norethisterone suppresses the hypothalamic–pituitary–gonadal axis (HPG axis) and hence has antigonadotropic effects. The estrogenic activity of norethisterone at high doses would also be expected to contribute to its antigonadotropic effects.
Congenital rubella syndrome (CRS) can occur in a developing fetus of a pregnant woman who has contracted rubella, usually in the first trimester. If infection occurs 0–28 days before conception, the infant has a 43% risk of being affected. If the infection occurs 0–12 weeks after conception, the risk increases to 81%. If the infection occurs 13–26 weeks after conception, the risk is 54% of the infant being affected by the disease. Infants are not generally affected if rubella is contracted during the third trimester, or 26–40 weeks after conception. Problems rarely occur when rubella is contracted by the mother after 20 weeks of gestation and continues to disseminate the virus after birth. It was discovered in 1941 by Australian Norman McAlister Gregg. Signs and symptoms
The classic triad for congenital rubella syndrome is:
Sensorineural deafness (58% of patients)
Eye abnormalities—especially retinopathy, cataract, glaucoma, and microphthalmia (43% of patients)
Congenital heart disease—especially pulmonary artery stenosis and patent ductus arteriosus (50% of patients)Other manifestations of CRS may include:

Spleen, liver, or bone marrow problems (some of which may disappear shortly after birth)
Intellectual disability
Small head size (microcephaly)
Low birth weight
Thrombocytopenic purpura
Extramedullary hematopoiesis (presents as a characteristic blueberry muffin rash)
Enlarged liver
Small jaw size
Skin lesions Children who have been exposed to rubella in the womb should also be watched closely as they age for any indication of:

Developmental delay
Autism
Schizophrenia
Growth retardation
Learning disabilities
Diabetes mellitus

Diagnosis
Prevention
Vaccinating the majority of the population is effective at preventing congenital rubella syndrome.