In vivo conversion of norethisterone to ethynyloestradiol in perimenopausal women

doi:10.1016/0960-0760(90)90342-I

The Journal of Steroid Biochemistry and Molecular Biology

Volume 37, Issue 2, October 1990, Pages 301-303

https://doi.org/10.1016/0960-0760(90)90342-I Get rights and content

Abstract

The extent to which norethisterone is converted to ethynyloestradiol is controversial. To investigate the conversion of norethisterone to ethynyloestradiol we have used a double isotope infusion technique to measure the conversion in vivo. The use of acids or bases was precluded to prevent possible artefactual formation of phenolic metabolites of norethisterone. Transfer constants for the conversion of norethisterone to ethynyloestradiol in two perimenopausal women were 2.26 and 2.34% as measured in blood and 2.27 and 0.38% in urine. Results from this study show that a small but significant proportion of norethisterone is converted to ethynyloestradiol in vivo.

References (26)

J.D. Townsley et al.
Mechanism of oestrogen biosynthesis. IV Ovarian metabolism of estr-4-ene-3,17-dione
Biochim. Biophys. Acta
(1967)
M. Urabe et al.
Aromatization of norethisterone to ethynyloestradiol in human adult liver
Steroids
(1987)
M.J. Reed et al.
The conversion of androstenedione to oestrone and production of oestrone in women with endometrial cancer
J. Steroid Biochem.
(1979)
P.G. Frost et al.
The aromatization of androstenedione by human adipose and liver tissue
J. Steroid Biochem.
(1980)
T.M. Mills et al.
The metabolic clearance rate and urinary excretion of oral contraceptive drugs
Am. J. Obstet. Gynaec.
(1974)
C. Longcope et al.
The metabolism of synthetic estrogens in non-users and users of oral contraceptives
Steroids
(1975)
K.F. Fotherby et al.
Metabolism of synthetic steroids
Adv. Steroid Biochem. Pharmac.
(1972)
H. Breuer et al.
Ausscheidung von 17-ketosteroiden, 17-ketogen und ostrogen beim mencschen und gaben von 17-athynyl-19-nortestosteron-estern
Acta Endocr.
(1960)
J.B. Brown et al.
Urinary oestrogen metabolites of 19-norethisterone and its esters
S. Kamyab et al.
Metabolism of [4-¹⁴C]norethisterone in women
J. Endocr.
(1968)

J.D. Townsley et al.

A new placental metabolite of oestr-4-ene-3,17-dione: A possible source of error in oestrogen estimation

Biochem. J.

(1966)

S.F. Sisenwine et al.

Phenolic metabolites of DL-norgestrel: a method for the removal of 1-hydroxylated metabolites, potential sources of phenolic artifacts

Acta Endocr.

(1964)

R.L. Barbieri et al.

Aromatization of norethisterone to ethinylestradiol by human placental microsomes

J. Clin. Endocr. Metab.

(1983)

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The detection of 19 norandrosterone (19-NA) in a competitor's urine sample is taken as prima facie evidence of administration of nandrolone or other 19-norsteroid but a potential problem is that administration of norethisterone, a progestogen used for menstrual disorders and for hormonal contraception, also results in the excretion of 19-NA that can exceed the laboratory reporting threshold of 2 ng/mL. The contribution of norethisterone to urinary 19-NA with and without 19-norandrostenedione, a known norethisterone tablet impurity, requires evaluation. Preparations containing, either <2 ng or 1 μg 19-norandrostenedione impurity per 5 mg of norethisterone, administered to female volunteers (n = 10) in doses comparable to those used for menstrual disorders (5 mg three times daily for 10 days), resulted in maximal 19-NA concentrations of 51 and 63 ng/mL, respectively. The maximal concentration of 19-NA, 2 h post-administration of a single 1 μg dose of 19-norandrostenedione, was 2.4 ng/mL. These results prove unequivocally that norethisterone is metabolized to 19-NA and that there is only a minor contribution from the impurity 19-norandrostenedione. Administration to women (n = 30) of a single contraceptive tablet containing norethisterone (1 mg) with one of the highest proportions of the impurity 19-norandrostenedione (∼0.5 μg, 0.05%, w/w) resulted in a urinary 19-NA concentration of 9.1 ng/mL, with a maximum concentration ratio of 19-NA to the norethisterone metabolite 3α,5β-tetrahydronorethisterone of 0.36. We provide data that should remove the need for time-consuming follow-up investigations to consider whether doping with 19-norandrogens has occurred.
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To exclude that aromatization plays a role in the estrogenic activity of tibolone, we studied the effect tibolone and metabolites on the aromatization of androstenedione and the aromatization of tibolone and its metabolites to 7α-methyl-17α-ethynylestradiol (7α-MEE) by human recombinant aromatase. Testosterone (T), 17α-methyltestosterone (MT), 19-nortestosterone (Nan), 7α-methyl-19-nortestosterone (MENT) and norethisterone (NET) were used as reference compounds. Sensitive in vitro bioassays with steroid receptors were used to monitor the generation of product and the reduction of substrate. LC-MSMS without derivatization was used for structural confirmation.
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Short communicationIn vivo conversion of norethisterone to ethynyloestradiol in perimenopausal women

Abstract

Biochim. Biophys. Acta

Steroids

J. Steroid Biochem.

J. Steroid Biochem.

Am. J. Obstet. Gynaec.

Steroids

Metabolism of synthetic steroids

Adv. Steroid Biochem. Pharmac.

Ausscheidung von 17-ketosteroiden, 17-ketogen und ostrogen beim mencschen und gaben von 17-athynyl-19-nortestosteron-estern

Acta Endocr.

Urinary oestrogen metabolites of 19-norethisterone and its esters

Metabolism of [4-14C]norethisterone in women

J. Endocr.

A new placental metabolite of oestr-4-ene-3,17-dione: A possible source of error in oestrogen estimation

Biochem. J.

Phenolic metabolites of DL-norgestrel: a method for the removal of 1-hydroxylated metabolites, potential sources of phenolic artifacts

Acta Endocr.

Aromatization of norethisterone to ethinylestradiol by human placental microsomes

J. Clin. Endocr. Metab.

Short communication
In vivo conversion of norethisterone to ethynyloestradiol in perimenopausal women

Metabolism of [4-¹⁴C]norethisterone in women