**2.5 The normative role of androgens for physiological and psychological processes**

Androgens have well-known growth-enhancing effects to regulate development and functional aspects of the reproductive, central nervous system, skeletal, and cardiovascular systems throughout the lifespan (thru the lifespan that include patterns of androgen secretion. Supported by early investigations in the field [5], the capacity of androgens that are secreted from the testes during early pre- or peri-natal development may "organize" the central nervous system, including the

**Figure 3.** *Mechanism of action of finasteride.*

neural control of post-pubertal patterns of androgen release, as well as sensitivity of specific brain structures to androgens in adulthood for behaviors. From birth until sexual maturation, androgen levels are typically low. At puberty, androgen levels increase and remain high until midlife when androgen levels begin to decline. Many of the targets of androgens have been highlighted by changes in the tissues' functions with decline in androgens. Among people, this is often assessed by determining age-related changes in function. Unlike the precipitous decline in ovarian function with reproductive senescence that is observed among women, men experience a decade-by-decade decline in androgens. **Figure 4** displays the data from Handelsman et al. 1995 and show the decline in these hormones with age [6]. This decline is termed "andropause" and, although the nature of the decline in steroids is different from that observed during the menopause of women, both situations have clear symptomology associated with steroid decline at this time. For example, decline in bioactive androgens in men with aging is associated with diminished libido, fatigue, decreased muscle mass, osteoporosis, depression, and/or cognitive dysfunctions. Given the aging population and robust effect that androgens have on physiological and psychological function, there is now great interest in the role of androgen-based therapies to obviate some of these symptoms. Moreover, there are younger populations that are using synthetic androgens, such as illicit anabolic androgenic steroids (AAS), with or without other drugs to alter steroid metabolism (finasteride). A serious concern that limits the use of steroid-based treatments in men is their potential to increase risk for prostate pathologies as well as psychological effects (**Figure 5**).
