Testosterone

About: Testosterone is a research topic. Over the lifetime, 23258 publications have been published within this topic receiving 808079 citations. The topic is also known as: 4-androsten-17beta-ol-3-one & 4-Androsten-3-one-17b-ol.

Induction of Testicular Aromatization by Luteinizing Hormone in Mature Rats

Abstract: The hormonal regulation of testicular aromatization and the intratesticular site of estradiol synthesis was investigated in adult rats. To determine testicular aromatization, cell-free homogenates of whole testes, isolated interstitial tissue, and seminiferous tubules were incubated with [3H]testosterone. 3H-Labeled estrogens were isolated and final identity was established by recrystallization of the product with authentic 17β-estradiol or estrone. No 3H-labeled estrogens could be identified in testicular incubations from saline-treated rats. In contrast, similar incubations from rats treated for 6 days with hCG or LH had the capacity to aromatize testosterone to estradiol. Testicular homogenates from rats treated with 4.4 IU hCG/day synthesized 4.76 pg estradiol/mg protein, which represents approximately 280 pg estradiol synthesized/testis during a 3-h incubation. In incubations of cell-free homogenates of isolated testicular compartments from hCG-treated rats, aromatase activity was demonstrated only i...

Low testosterone levels are associated with coronary artery disease in male patients with angina.

Abstract: Historically, high androgen levels have been linked with an increased risk for coronary artery disease (CAD). However, more recent data suggest that low androgen levels are associated with adverse cardiovascular risk factors, including an atherogenic lipid profile, obesity and insulin resistance. The aim of the present study was to evaluate the relationship between plasma sex hormone levels and presence and degree of CAD in patients undergoing coronary angiography and in matched controls. We evaluated 129 consecutive male patients (mean age 58+/-4 years, range 43-72 years) referred for diagnostic coronary angiography because of symptoms suggestive of CAD, but without acute coronary syndromes or prior diagnosis of hypogonadism. Patients were matched with healthy volunteers. Out of 129 patients, 119 had proven CAD; in particular, 32 of them had one, 63 had two and 24 had three vessel disease, respectively. Patients had significantly lower levels of testosterone than controls (9.8+/-6.5 and 13.5+/-5.4 nmol/l, P<0.01) and higher levels of gonadotrophin (12.0+/-1.5 vs 6.6+/-1.9 IU/l and 7.9+/-2.1 vs 4.4+/-1.4, P<0.01 for follicle-stimulating hormone and luteinizing hormone, respectively). Also, both bioavailable testosterone and plasma oestradiol levels were lower in patients as compared to controls (0.84+/-0.45 vs 1.19+/-0.74 nmol/l, P<0.01 and 10.7+/-1.4 vs 13.3+/-3.5 pg/ml, P<0.05). Hormone levels were compared in cases with one, two or three vessel disease showing significant differences associated with increasing severity of coronary disease. An inverse relationship between the degree of CAD and plasma testosterone levels was found (r=-0.52, P<0.01). In conclusion, patients with CAD have lower testosterone and oestradiol levels than healthy controls. These changes are inversely correlated to the degree of CAD, suggesting that low plasma testosterone may be involved with the increased risk of CAD in men.

Dihydrotestosterone formation in fetal tissues of the rabbit and rat.

Abstract: The rate of conversion of testosterone- l,2-3H to dihydrotestosterone-3H has been measured in a variety of tissues in rabbit embryos from 17 days of development to 3 days following birth and in rat embryos from 15 days of gestation to 4 days after delivery. In the rabbit embryo dihydrotestosterone formation was rapid only in the urogenital sinus and urogenital tubercle of both sexes at the earliest stages studied and was not measurable in wolffian and mullerian ducts until after gender identification was easily demonstrable. A similar pattern of development was observed in the rat embryo. These findings suggest that the capacity to form dihydrotestosterone in urogenital sinus and tubercle is not the result of androgen action but rather an inherent or obligatory property of the tissue and may fulfill in part the function of an initial androgen receptor in these organs. In contrast, in the mullerian and wolffian ducts the ability to form dihydrotestosterone appears to be acquired after the initial stages of...

Testosterone-Binding Levels in the Serum of Women During the Normal Menstrual Cycle, Pregnancy, and the Post-partum Period

Abstract: The testosterone-binding level (or activity) in human serum, as determined by our technique based on the principle of equilibrium dialysis but utilizing Sephadex G-25, remained low and relatively constant during the normal menstrual cycle. It rose steeply, however, during the first trimester of pregnancy and gradually thereafter, attaining at term a level about 2–3 times that obtained in the nonpregnant state; a rapid return to nonpregnancy levels occurred after delivery. These observations suggest that the testosterone-binding level is directly related to endogenous steroid sex hormone production; estrogen may be particularly important in this respect since elevated testosterone-binding levels were also observed in men with prostatic cancer receiving estrogen therapy.