Testosterone role

Androgens act via the AR and play an important role in the development and differentiation of the male sexual organ. Furthermore, they are involved in several diseases, the most important being partial and complete androgen insensitivity syndrome (AIS formerly known as the testicular feminization syndrome), spinal and bulbar muscle atrophy (SBMA Kennedy s disease), and the neoplastic transformation of the prostate. The two natural occurring androgens are testosterone (T) and the... 

McCormick K, Abdel-Rahman MS. 1991. The role of testosterone in trichloroethylene penetration in vitro. Environ Res 54 82-92. 

Testosterone also plays a significant albeit complex role in erectile function. Testosterone is responsible for much of a man s libido. With low serum concentrations, libido declines. Additionally, testosterone helps with stabilization of intracavernosal levels of nitric oxide synthase, the enzyme responsible for triggering the nitric oxide cascade. Interestingly, some patients with low or borderline low serum concentrations of testosterone will have normal erectile function, while some with normal levels will have dysfunction. 

Leonard, S. T., Alizadeh-Naderi, R., Stokes, K., and Ferkin, M. H. (2005) The role of prolactin and testosterone in mediating seasonal differences in the self-grooming behavior of male meadow voles, Microtus pennsylvanicus. Physiol. Behav. 85 461 —468. 

The follicular phase covers the development of the follicle, which involves an increase in its size due to an increase in follicular fluid, growth of the ovum (i.e. an increase in the contents of RNA and protein) and an increase in the number of cells that surround the ovum. These cells are of two types, the granulosa and the thecal cells. The role of these cells is to synthesise and secrete the steroid hormones oestrogens (mainly oestradiol). The precursor molecule for their synthesis is cholesterol. There is a division of labour between these cells the thecal cells convert cholesterol into the male sex hormones androstenedione and testosterone, which are released into the blood to be taken up by the granulosa cells where they are converted to the oestrogens (Figure 19.8). For details of pathways, see Appendix 19.1. 

A long-held view is that oestrogens are the hormones that control reproductive activity in the female and that androgens control the activity in the male. Although this is broadly the case, such a complete separation is too simple. For example, testosterone is secreted by the thecal cells in the ovary and although some is taken up by the granulosa cells for conversion to an oestrogen, some remains in the blood, where it has several roles (e.g. stimu-... 

Effects in the adult In the adult, testosterone maintains spermatogenesis. It also influences sexual interest, arousal and behaviour. Nonetheless, although testosterone plays a role in sexual behaviour, social, environmental and emotional factors are also important. Indeed, neither testosterone in the male nor oestradiol in the female is essential for sexual interactions in humans. 

Grant JK, Mingnell J, Taylor P, Weiss M. (1971) A possible role of zinc in the metabolism of testosterone by the prostate gland. Biochem J125 21P... 

At the endocrinological level, the VNO mediates the surge of luteinizing hormone and testosterone in males after exposure to females. This surge does not occur if a male with deafiferentiated VNO is exposed to an anesthetized female or her urine (Wysocki etal., 1983). But VNO-deafferentiated males will show a surge in luteinizing hormone in response to awake females (Coquelin etal., 1984). In female mice, stimulation of the VNO by male urinary cues activates the limbic system (discussed in Ch. 8). The roles of the VNO in the behavior of some rodents are listed in Table 5.3. 

Donna Toufexis completed her doctoral training in neuroendocrinology at McGill University in Montreal, Canada, and postdoctoral training at Concordia University in Montreal. Toufexis is presently a research associate at the Center for Behavioral Neuroscience (CBN) at Emory University in Atlanta. Her primary research interest is the characterization of brain mechanisms that govern fear and anxiety. In particular, Toufexis is interested in the role that neuroactive hormones estrogen, testosterone, and oxytocin play in the regulation of fear and anxiety. 

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