Metabolism of testosterone and androstenedione in normal and ovariectomized women

Abstract

A B S T R A C T Metabolic clearance rates of testosterone (MCRT) and androstenedione (MCRA) were determined twice during the same cycle in six normal women, using a constant infusion of testosterone-2H and androstenedione-"C. Nonlabeled steroids served as internal standards. Plasma concentrations of testosterone (iT) and androstenedione (iA) were measured, and the blood production of testosterone (PBT) and of androstenedione (PBA) were calculated. The interconversions of these two steroids were also estimated. Six ovariectomized women were studied in the same manner. For testosterone, the mean i in the normal women was not significantly different from that in the ovariectomized subjects, whereas the MCRT and PET were significantly lower in the ovariectomized subjects. For androstenedione, the mean MCRA values of the two groups of subjects were not different, whereas the iA and PBA in the normal women were about double those in the ovariectomized subjects. In comparing the follicular and luteal phases of the menstrual cycle in four of six subjects there was no difference in iT, MCRT, or PBT, whereas iA, MCRA, and PBA were increased in the luteal phase. In one ovariectomized woman infused with testosterone and androstenedione at physiologic levels, MCRT doubled but MCRA remained the same. After six wk on estrogen, the same subject did not show any change in MCRT after infusion of testosterone. It is suggested that MCRT depends on PBT and on plasma binding of testosterone which is partly estrogen dependent.

Plasma Concentrations and Rates of Plasma Clearance and Production of Cortisol and Corticosterone in Healthy Persons and in Subjects with Asymptomatic and Clinical Diabetes Mellitus

“…Thus, it has also been possible to overeome the problems of the "isotope dilution (= urinary exeretion = single injeetion) teehnique" (Lazarus, 1962;Fukushima, Bradlow, HeIlman andGallagher, 1968, 1969;Kowarski, Lawrence, Hung and Migeon, 1969;Baüey and West, 1969;Kowarski, Kenny and Migeon, 1970). The eonstant infusion method has meanwhile been sueeessfully employed for the estimation of metabolie clearanee-rates of aldosterone (TaU, TaU, Little and Laumas,196 I), of the androgens (Horton and TaU, 1966;Lipsett, Wilson, Kirschner, Korenman, Fishman, Sarfaty and Bardin, 1966;Rivarola, Saez, Meyer, Jenkins, Migeon, 1966;Abraham, Lobotsky and Lloyd, 1969) and the estrogens (Longcope, Layne and TaU, 1968), progesterone (Little, TaU, Tait and Erlenmeyer, 1966), and eortisol (Dodek, Segre and Klaiber, 1965;Segre, Friedrich, Dodek, Lloyd, Lobotsky, Levin and Klaiber, 1966). Studies on eortieosterone employing the eonstant infusion teehnique have not as yet eome to our attention.…”

Corpus luteum dysfunction and the epidemiology of breast cancer: A reconsideration

“…The plasma levels and metabolic clearance of androstenedione are higher during the luteal phase of the normal menstrual cycle (15). Inadequate corpus luteum function would be expected to result in diminished urinary androgen secretion and might thus explain the lowered androgen metabolites in the urine of breast cancer patients.…”

Update on nandrolone and norsteroids: how endogenous or xenobiotic are these substances?

“…1) in the biological synthesis of estrogens from obligatory androgens precursors in all species, including man (Desgrez andMalmejac 1970, Dumasia et al 1989;Farnsworth 1966;Garrett et al 1991;Hagensen-Jetne et al 2000;Hillier et al 1980;Le Bizec et al 1999;Perel and Killinger 1979;Reznik et al 1987;Short 1961Short , 1964Skinner and Akhtar 1969). However, aromatization of androgens by aromatase is controlled by an enzymic complex (P450 arom ) which presents in most cells, ovaries and placental microsomes excepted, a very small quantitative activity which does not even reach 0.1% biotransformation of the androgen substrates to estrogens (Abraham et al 1969;Bellino and Osawa 1974;Berkowitz et al 1984;Frisch et al 1980;Frost et al 1980;Hillier et al 1980;Kley et al 1980;Longcope et al 1972Longcope et al , 1976Longcope et al , 1983McDonald et al 1967;Nimrod and Ryan 1975;Payne et al 1976;Perel and Killinger 1979;Ryan 1959;Short 1961;Simpson et al 1993;Schweikert 1979;Thompson and Siiteri 1974). Although the normal and pathological molecular biology and physiopathological control of the aromatase complex activity are well advanced in animal and human, for both sexes, the actual chemical steps involved in estrogen synthesis are still under discussion.…”