Norethindrone (NET), or norethisterone, is a synthetic progestogen derived from testosterone and used in hormonal contraceptives, hormone replacement therapy, and treatment of gynecological disorders. Prodrugs of NET used in medications include norethindrone acetate (NETA) and norethindrone enanthate (NETE).
DrugBank Accession Number
KEGG Entry Number
Wikipedia Entry Name
White or yellowish white, odorless, crystalline powder
Zafar: 201-203 °C
IARC, Toxnet: 203-204 °C
Insoluble in water, soluble in chloroform and dioxane, sparingly soluble in acetone and anhydrous ethanol. Slightly soluble in diethyl ether.
Specific Optical Rotation
-32.0 to -37.0 (dried)
-31.7 °C in chloroform
GHS Hazard Code(s)
|Carcinogenicity||2||H351||Suspected of causing cancer if inhaled|
|Reproductive Toxicity||1A||H360FD||May damage fertility. May damage the unborn child|
|Reproductive Toxicity, Effects On or Via Lactation||H362||May cause harm to breast-fed children|
|Acute Dermal Toxicity||4||H312||Harmful in contact with skin|
|Acute Inhalation Toxicity||4||H332||Harmful if inhaled|
|Reproductive Toxicity||1B||H360||May damage fertility or the unborn child|
Not found to be mutagenic in the Ames Salmonella/microsome direct plate incorporation protocol.
Reports vary: Ahmad et al. reported it as non-genotoxic to human lymphocyte chromosomes as measured by chromosomal aberrations, sister chromatid exchanges, and cell growth kinetics. Martelli et al. suggested it could be a week genotoxin.
LD50, mouse oral: 6 g/kg
TDLo, human women oral: 42 mg/kg
Progesterone Receptor Activity
Androgen Receptor Activity
Estrogen Receptor Activity
Agonist and antagonist
Glucocorticoid Receptor Activity
Mineralocorticoid Receptor Activity
Elimination Half-Life (t1/2)
7-8 h (Stanczyk, Goodman & Gilman)
4.8 - 12.8 h (Toxnet)
Serum Protein Binding
> 95%, 61% to albumin, 36% to SHBG
Apparent Volume of Distribution
Estrone sulfatase inhibitor
Inhibition of Ovulation
Transformation of Endometrium
Sulfate and glucuronide conjugates of norethindrone and its metabolites are also present.
The epimer 19-noretiocholanolone may also be formed by metabolism of NET. Detection of 19-norandrosterone in an athlete's urine is taken as evidence of doping by nandrolone or another 19-steroid. However, this compound is a metabolite of norethindrone, and as a metabolite, it can be detected in quantities above the reporting threshold of 2 ng/mL.