Steroid dynamics under steady-state conditions.
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Abdomen↗
Biomedical subjects
C Longcope
Publications and source records attributed to C Longcope.
Conversion of blood androgens to estrogens in normal adult men and women.
Continuous infusions of Delta(4)-androstenedione-7-(3)H and testosterone-7-(3)H have been used to demonstrate that these androgens are converted to estrone and 17beta-estradiol, and contribute to the circulating blood levels of these estrogens in normal males and females. The conversion ratio (ratio of concentrations of radioactivity of free product steroid [chi(-PRO)] and free precursor steroid [chi(-PRE)], both corrected for recoveries, after an infusion of radioactive precursor steroid) for androstenedione (precursor) to estrone (product) is 0.013 in males and 0.007 in females, and the conversion ratio for testosterone (precursor) to estradiol (product) is 0.0018 in males and 0.005 in females. The transfer constant, [rho](BB) (AE1), for androstenedione conversion to estrone ([rho](BB) (AE1) = per cent of infused androstenedione, precursor, converted to estrone, product, when infusion and measurement are both in blood) is 1.35% in males and 0.74% in females, and the transfer constant, [rho](BB) (TE2), for testosterone conversion to estradiol is 0.39% in males and 0.15% in females. Whether measured as conversion ratio or transfer constant, the peripheral aromatization of androstenedione takes place to a greater degree than that of testosterone, and, for the respective androgens, both the conversion ratio and [rho](BB) value are greater in males than females. For the androgen interconversions, [rho](BB) (AT) is 4.5% in males and 2.2% in females; [rho](BB) (TA) is 8.2% in males and 12.0% in females. Studies on the distribution coefficients (effective concentration in red cells/plasma) for precursor radioactivity were also made. In both males and females the distribution coefficient for androstenedione is 0.16-0.17 while that of testosterone is 0.01-0.03.
Adult↗
Metabolic clearance rates and interconversions of estrone and 17beta-estradiol in normal males and females.
The continuous infusion of (3)H-6,7-estrone and (3)H-6,7-estradiol has been used to study the metabolic clearance rate (MCR), the interconversions, and the red cell uptake of these steroids in normal males and females. The whole blood MCR of estrone is 1,990 +/- 120 liters per day/m(2) (SE) in males and 1,910 +/- 100 liters per day/m(2) in females. The whole blood MCR of estradiol is 1,600 +/- 80 liters per day/m(2) in males and 1,360 +/- 40 liters per day/m(2) in females. The values in females do not vary significantly when studied in the follicular or luteal phase of the cycle. At least 35% of the total estrone metabolism in both sexes is extrasplanchnic and at least 25% of the total estradiol metabolism in males, and 15% in females is extrasplanchnic. The [rho](BB) (2,1) [transfer constant of estradiol to estrone, which is equivalent to the fraction of the precursor (estradiol) converted to the product (estrone) when both the infusion of the precursor and the measurement of the product are in peripheral blood] is 15%; and the [rho](BB) (1,2) [transfer constant of estrone to estradiol, which is equivalent to the fraction of the precursor (estrone) converted to product (estradiol) when both the infusion of the precusor and the measurement of the product are in peripheral blood] is 5% in both males and females. Our findings concerning the radioactivity in whole blood, as measured by our procedure, were the following: 15-20% of estrone in both sexes and 15% of estradiol in males is associated with red cells. Only 2% of the whole blood radioactivity of estradiol in females is associated with red cells. Changes in the distribution of radioactivity between plasma and red cells will influence the MCR as calculated from plasma, but not as calculated from whole blood.
Journal Article↗
Peripheral aromatization: studies on controlling factors.
Using constant infusions of 3H-labeled androgens and 14C-labeled estrogens with measurements of radiolabeled estrogens in blood and/or urine we have carried out studies on the peripheral aromatization of androgens in humans, nonhuman primates, sheep, and rabbits. In the human, aromatization is increased in women as they become postmenopausal, although the mechanism remains uncertain. In humans and cynomolgus monkeys the administration of ACTH and/or glucocorticoids does not increase peripheral aromatization, but results in a slight decrease in the aromatization of androstenedione. The administration of l-thyroxine to cynomolgus monkeys increases peripheral aromatization of androstenedione from basal, 1.16 +/- 0.15%, to 1.71 +/- 0.14% probably due to increased tissue blood flow. The aromatization of testosterone is not affected, probably due to an increase in sex hormone-binding globulin. Peripheral aromatization occurs to a similar degree in humans, rhesus and cynomolgus monkeys, and baboons, but is much lower in sheep and rabbits. The compound 10-(2-propynyl)-estr-4-ene-3,17-dione is an effective inhibitor of the peripheral aromatization of both androstenedione and testosterone.
Adrenocorticotropic Hormone↗
Endocrine function of the postmenopausal ovary.
The ovaries of postmenopausal women are smaller than those of premenopausal women and consist primarily of stromal cells. These cells have receptors for, and respond to, gonadotropins and secrete testosterone and lesser amounts of other androgens and estrogens. The ovaries of some postmenopausal women contain P-450 aromatase and secrete estradiol. There is little evidence that inhibins A or B are secreted by postmenopausal ovaries.
Androgens↗
Is there an association between menopause status and sexual functioning?
OBJECTIVE: The purpose of this study was to address whether: (1) there is an association between menopause status and various aspects of sexual functioning, and (2) the relative contributions of menopause status and other variables to various aspects of sexual functioning. DESIGN: Analyses are based on 200 women from the Massachusetts Women's Health Study II, a population-based sample of women transitioning through the menopause who were not HRT users, who had not had a surgical menopause, and who had partners. The women were classified as pre-, peri-, or postmenopausal according to menstrual cycle characteristics. Estradiol, estrone, and follicle-stimulating hormone were also measured. Sexual functioning was measured in terms of satisfaction, desire, frequency of sexual intercourse, belief that interest declines with age, arousal compared with a younger age, difficulty reaching orgasm, and pain. Predictor variables included sociodemographics, health, vasomotor symptoms, psychological variables, partner variables, and lifestyle behaviors. RESULTS: Menopause status was significantly related to lower sexual desire, a belief that interest in sexual activity declines with age, and women's reports of decreased arousal compared with when in their 40s. Menopause status was unrelated to other aspects of sexual functioning in either unadjusted or multiple regression analyses. In analyses in which log estradiol (E2) was included in addition to menopause status, log E2 was only related to pain. In multiple regression analyses, other factors such as health, marital status (or new partner), mental health, and smoking had a greater impact on women's sexual functioning than menopause status. CONCLUSIONS: Menopause status, but not E2, is related to some, but not all, aspects of sexual functioning. This may be due to menopause per se or other factors associated with menopause and aging (e.g., increased sexual dysfunction among aging men). Menopause status has a smaller impact on sexual functioning than health or other factors.
Aging↗
Can follicle-stimulating hormone be used to define menopausal status?
OBJECTIVE: To assess the ability of the level of follicle-stimulating hormone (FSH) to distinguish among premenopausal, perimenopausal, and postmenopausal women. METHODS: We examined cross-sectional and longitudinal data from the second phase of the Massachusetts Women's Health Study (1986 to 1995), a population-based cohort of 427 premenopausal and perimenopausal women identified from the first phase of the Massachusetts Women's Health Study (1981 to 1986). RESULTS: Boxplots of FSH levels throughout the menopausal transition displayed considerable overlap. Logistic regressions and their resulting receiver operating characteristic curves further demonstrated that, although FSH is a statistically significant predictor of menopausal status, no single value of FSH is expedient for distinguishing premenopausal from perimenopausal or perimenopausal from postmenopausal women. CONCLUSION: FSH alone is not an effective predictor of transition into the perimenopausal or postmenopausal period. Specifically, the frequently recommended FSH cutoff of 40 IU/L is inappropriate by itself for clinical determination of postmenopausal status.
Journal Article↗