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.

hCG Binding and Stimulation of Testosterone Biosynthesis in the Human Fetal Testis

Abstract: The role of hCG in the regulation of testicular steroid production in human fetuses from 14 to 20 weeks gestational age was studied. Saturable binding of 125I-hCG to testicular homogenates was demonstrated, and physiologic concentrations of hCG were able to stimulate testosterone formation in testicular minces without the addition of exogenous precursors. In five fetses of 16-20 weeks gestational age, the capacity to bind hCG varied from 25.6 to 42.2 pg/mg wet tissue. The association constant of binding was 1.07+/-0.12 X 10(10) M-1. Testicular minces from six other fetuses (gestational age 14-19 weeks) were incubated in the presence of concentrations of 0, 0.5, 5 or 50 ng/ml NIH-hCG (1 mg=10,000 IU), which are within the physiologic range. Preincubation of 30 min in excess buffer was necessary to observe clear differences in testosterone production rates between controls and hCG stimulated testicular tissues. The greatest increase in testosterone production occurred when the hCG concentration was increased from 0.5 to 5 ng/ml. Little additional stimulation was observed at a concentration of 50 ng/ml. Maximal production rates of up to 12 ng/mg tissue/h were seen. It is concluded that human fetal testes bind hCG, and that physiologic levels of hCG stimulate fetal testicular testosterone formation in vitro at this stage of gestation.

Endocrine profile in serum and follicular fluid differs after ovarian stimulation with HP-hMG or recombinant FSH in IVF patients

Abstract: BACKGROUND: Highly purified menotrophin (HP-hMG) has been associated with fewer oocytes retrieved and a higher proportion of top-quality embryos compared with recombinant FSH (rFSH). METHODS: A randomized, assessor-blind, multinational trial in 731 women undergoing IVF after stimulation with HP-hMG (MENOPUR) (n = 363) or rFSH (GONAL-F) (n = 368) following a long GnRH agonist protocol was conducted. Blood was collected before, during and after stimulation. Fluid was collected from follicles ≥17 mm. RESULTS: Serum androstenedione, total testosterone and free androgen index (FAI) were higher (P < 0.001) with HP-hMG than with rFSH after starting stimulation. At the end of stimulation, serum estradiol was higher (P = 0.031) with HP-hMG, whereas progesterone was higher (P < 0.001) with rFSH, even after adjusting for ovarian response. Serum LH was not different between treatments. Mean mid- and end-follicular hCG levels in the HP-hMG group were 2.5 and 2.9 IU/I, respectively. Follicular fluid levels of FSH, LH, hCG, androstenedione, testosterone, FAI and estradiol and ratios of estradiol: androstenedione, estradiol: total testosterone and estradiol: progesterone were higher (P < 0.001) with HP-hMG, whereas progesterone was higher (P < 0.001) with rFSH. CONCLUSION: Major differences in serum and follicular fluid endocrine profile exist after stimulation with HP-hMG or rFSH. Exogenous LH activity induces a differential endocrine environment influencing oocyte quantity and quality, which may be of relevance for clinical outcome.

Evidence of Limited Contributions for Intratumoral Steroidogenesis in Prostate Cancer

Abstract: Androgen-deprivation therapy for prostate cancer (PC) eventually leads to castration-resistant PC (CRPC). Intratumoral androgen production might contribute to tumor progression despite suppressed serum androgen concentrations. In the present study, we investigated whether PC or CRPC tissue may be capable of intratumoral androgen synthesis. Steroidogenic enzyme mRNAs were quantified in hormonally manipulated human PC cell lines and xenografts as well as in human samples of normal prostate, locally confined and advanced PC, local nonmetastatic CRPC, and lymph node metastases. Overall, the majority of samples showed low or absent mRNA expression of steroidogenic enzymes required for de novo steroid synthesis. Simultaneous but low expression of the enzymes CYP17A1 and HSD3B1, essential for the synthesis of androgens from pregnenolone, could be detected in 19 of 88 patient samples. Of 19 CRPC tissues examined, only 5 samples expressed both enzymes. Enzymes that convert androstenedione to testosterone (AKR1C3) and testosterone to dihydrotestosterone (DHT; SRD5A1) were abundantly expressed. AKR1C3 expression was negatively regulated by androgens in the experimental models and was increased in CRPC samples. Expression of SRD5A1 was upregulated in locally advanced cancer, CRPC, and lymph node metastases. We concluded that intratumoral steroid biosynthesis contributes less than circulating adrenal androgens, implying that blocking androgen production and its intraprostatic conversion into DHT, such as via CYP17A1 inhibition, may represent favorable therapeutic options in patients with CRPC.

Plasma cortisol, androstenedione, testosterone and luteinizing hormone in running exercise of different intensities

Abstract: Changes in plasma cortisol, androstenedione, testosterone and luteinizing hormone (LH) were measured in five young male sprinters after maximal short-term running and in five young male long-distan...