Topic
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.
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TL;DR: The results of this study demonstrate that androgen deprivation alters the functional responses and structure of erectile tissue.
Abstract: We investigated, in a rabbit model, the effects of castration and testosterone replacement on: 1) the hemodynamics of the corpus cavernosum; 2) α-1 adrenergic receptor protein expression; 3) neural NO synthase protein expression and activity; 4) phosphodiesterase type 5 activity; and 5) trabecular smooth muscle/connective tissue balance. One week after bilateral orchiectomy, animals were treated for 7 days with vehicle alone, testosterone, or estradiol. Intact control animals received vehicle only. Systemic arterial blood and intracavernosal pressures (ICP) were measured in each animal before and after electrical stimulation of the cavernosal nerve.α 1-adrenergic receptor protein expression was determined by ligand binding studies. NO synthase expression and activity were determined by Western blot analyses and conversion of l-arginine to citrulline, respectively. Phosphodiesterase type 5 activity was determined by hydrolysis of guanosine 3′,5′-cyclic monophosphate (cGMP) in tissue extracts in the absence...
292 citations
TL;DR: The mass action equation and equilibrium dialysis are the preferred methods for use in diagnosing androgen deficiency in women.
Abstract: Androgen deficiency in women is increasingly recognized as a new clinical syndrome and has raised our awareness of the importance of accurate and well-validated measurements of serum free testosterone (T) concentrations in women. Therefore, we compared serum free T levels measured by equilibrium dialysis to those measured by a direct RIA (analog method) and to those calculated from the law of mass action (requires the measurement of total T and SHBG). We also calculated the free androgen index, 100 x T/SHBG, as a simple index known to correlate with free T. Subjects were 147 women with variable androgen and estrogen statuses. All were studied three times in 1 month and included women 1) with regular menses (estrogen positive, T positive), 2) more than 50 yr old and not receiving estrogen (estrogen negative, T positive), 3) receiving estrogen (estrogen positive, T negative), and 4) with severe androgen deficiency secondary to hypopituitarism (estrogen negative, T negative). Calculated values for free T using the laws of mass action correlated well with those obtained from equilibrium dialysis (r = 0.99; P < 0.0001). However, the agreement depended strongly on the specific assays used for total T and SHBG. In contrast, the direct RIA method had unacceptably high systematic bias and random variability and did not correlate as well with equilibrium dialysis values (r = 0.81; P < 0.0001). In addition, the lower limit of detection was higher for the direct RIA than for equilibrium dialysis or calculated free T. Free androgen index correlates well with free T by equilibrium dialysis (r = 0.93; P < 0.0001), but is a unitless number without reference to the physical reality of free T. We conclude that the mass action equation and equilibrium dialysis are the preferred methods for use in diagnosing androgen deficiency in women.
292 citations
TL;DR: The steroid- and tissue-specificity of the cell-free systems strongly suggests that 5α-dihydrotestosterone plays a central role in the retention of an androgen receptor protein by prostate nuclei in vivo.
291 citations
TL;DR: Evidence of a covariation between circulating levels of estrogen and testosterone and certain affects in healthy women is provided, including depression scores of all oophorectomized women.
291 citations
TL;DR: Using mice in which the genetic sex of the brain was independent of gonadal phenotype, it was found that XY and XX brain cells differed in phenotype, indicating that a brain cell's complement of sex chromosomes may contribute to its sexual differentiation.
Abstract: Sex differences in the brain are caused by differences in gonadal secretions: higher levels of testosterone during fetal and neonatal life cause the male brain to develop differently than the female brain. In contrast, genes encoded on the sex chromosomes are not thought to contribute directly to sex differences in brain development, even though male (XY) cells express Y-chromosome genes that are not present in female (XX) cells, and XX cells may have a higher dose of some X-chromosome genes. Using mice in which the genetic sex of the brain (XX versus XY) was independent of gonadal phenotype (testes versus ovaries), we found that XY and XX brain cells differed in phenotype, indicating that a brain cell's complement of sex chromosomes may contribute to its sexual differentiation.
290 citations