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.

Androgen Levels in Adult Females: Changes with Age, Menopause, and Oophorectomy

Abstract: Context: Changes in androgen levels across the adult female life spanandtheeffectsofnaturalmenopauseandoophorectomyhavenot been clearly established. Objective: The objective of this study was to document the effects of age on androgen levels in healthy women and to explore the effects of natural and surgical menopause. Design, Setting, and Participants: A cross-sectional study was conducted of 1423 non-healthcare-seeking women, aged 18–75 yr, randomly recruited from the community over 15 months. Main Outcome Measures: Serum levels by age of total testosterone (T), calculated free T, dehydroepiandrosterone sulfate, and androstenedione in a reference group of women free of confounding factors. Women in the reference group had no usage of exogenous steroid therapy; no history of tubal ligation, hysterectomy, or bilateral oophorectomy; and no hyperprolactinemia or polycystic ovarian syndrome. The effects of natural and surgical menopause on sex steroid levels were also examined. Results:Inthereferencepopulation(n595),totalT,calculatedfree T, dehydroepiandrosterone sulfate, and androstenedione declined steeply with age (P 0.001), with the decline of each being greater in the earlier than the later decades. Examination of serum androgen levels by year in women aged 45–54 yr showed no independent effect of menopausal status on androgen levels. In women aged 55 yr or older, those who reported bilateral oophorectomy and were not on exogenous steroids had significantly lower total T and free T levels than women 55 yr or older in the reference group. Conclusions: We report that serum androgen levels decline steeply intheearlyreproductiveyearsanddonotvarybecauseaconsequence of natural menopause and that the postmenopausal ovary appears to be an ongoing site of testosterone production. These significant variationsinandrogenswithagemustbetakenintoaccountwhennormal ranges are reported and in studies of the role of androgens in women. (J Clin Endocrinol Metab 90: 3847–3853, 2005)

A role for oestrogens in the male reproductive system

Abstract: Oestrogen is considered to be the 'female' hormone, whereas testosterone is considered the 'male' hormone. However, both hormones are present in both sexes. Thus sexual distinctions are not qualitative differences, but rather result from quantitative divergence in hormone concentrations and differential expressions of steroid hormone receptors. In males, oestrogen is present in low concentrations in blood, but can be extraordinarily high in semen, and as high as 250 pg ml(-1) in rete testis fluids, which is higher than serum oestradiol in the female. It is well known that male reproductive tissues express oestrogen receptors, but the role of oestrogen in male reproduction has remained unclear. Here we provide evidence of a physiological role for oestrogen in male reproductive organs. We show that oestrogen regulates the reabsorption of luminal fluid in the head of the epididymis. Disruption of this essential function causes sperm to enter the epididymis diluted, rather than concentrated, resulting in infertility. This finding raises further concern over the potential direct effects of environmental oestrogens on male reproduction and reported declines in human sperm counts.

Sex hormones, immune responses, and autoimmune diseases. Mechanisms of sex hormone action

Abstract: Immune reactivity is greater in females than in males. In both experimental animals and in man there is a greater preponderance of autoimmune diseases in females, compared with males. Studies in many experimental models have established that the underlying basis for this sex-related susceptibility is the marked effects of sex hormones. Sex hormones influence the onset and severity of immune-mediated pathologic conditions by modulating lymphocytes at all stages of life, prenatal, prepubertal, and postpubertal. However, despite extensive studies, the mechanisms of sex hormone action are not precisely understood. Earlier evidence suggested that the sex hormones acted via the thymus gland. In recent years it has become apparent that sex hormones can also influence the immune system by acting on several nonclassic target sites such as the immune system itself (nonthymic lymphoid organs), the central nervous system, the macrophage-macrocyte system, and the skeletal system. Immunoregulatory T cells appear to be most sensitive to sex hormone action among lymphoid cells. Several mechanisms of action of sex hormones are discussed in this review. The possibility of using sex hormone modulation of immune responses for the treatment of autoimmune disorders is a promising area for future investigation.